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CHARLOTTE, N.C. — The training center has a warehouse feel, with exposed ductwork and cinder block walls. Box fans are blowing on a midsummer's day, but the thick air does not seem to move.

Steve Smith Sr. wears a cotton hoodie soaked through with sweat, and his skin looks like it's slathered in baby oil. In between most sets, he bends over, hands on knees. After one set, he lies on his back on the floor.

Time to go again—one-legged jumps on black Styrofoam blocks. He gets about halfway through the set and abruptly stops. He gives his trainer a look and walks swiftly out the open garage door, onto the dock. The rap music is loud but not loud enough to drown out the sound of retching.

Smith spends about a minute at the edge of the dock, aiming for a patch of weeds below. Then he walks back, wipes his face, gargles with water, gathers himself and takes a big gulp of Gatorade. He's ready to start again.

This isn't the first time this summer he could not keep his breakfast where it belonged. In fact, he admits, it's the third or fourth.

"It happens with competitive people who push themselves," Smith's trainer, Daniel Ancheta, says.

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"I know I've turned the corner when I puke," Smith says.

He expected that trying to come back from a career-threatening injury at the age of 37 would be difficult. So why does he push himself so far? With all he has accomplished, why not spare his mind and body and just call it a career?

"I wouldn't say the ability to overcome things is important to me," Smith says. "I'd say it's been the difference between life and death for me."

This is about being true to himself—and learning everything that means.

Smith's memory of the injury, sustained in November against the Chargers: He caught a pass, then felt a pull in the back of his leg, and then, "It was like my foot had no power. It was flapping." Then he went down, thinking dark thoughts. The trainers came running.

"What's the matter?" one said.

"I think I tore my Achilles," Smith said.

"Roll over, let's see," the trainer said, examining his right leg.

And then, in a whisper, "I think he's right."

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Smith draped a towel over his head, put his arms around the shoulders of trainers and hopped off the field.

It wasn't supposed to end that way.

He had a double rupture of his Achilles—an injury that his surgeon, renowned Charlotte orthopedist Robert Anderson, would later tell him was the first double rupture he ever had seen.

During surgery, the damage was photographed.

What did it look like?

"Raw, shredded chicken," Steve’s wife, Angie, says.

"Either the beginning or the end of something," Steve says.

On that day in November, it seemed to be the end—and not the ending Smith had intended.

The 2015 season was supposed be a celebration for Smith of the completion of a 15-year career. It was supposed to end with a bow, not his body looking like shredded chicken.

After some reflection, Smith decided he did not want his magnificent career to end that way. He would attempt a comeback at the age of 37.

If you have lasted in the NFL as long as Smith has, you know injuries. He previously had a sprained PCL. He has broken his arm, his neck, his leg and a few fingers. There was one documented concussion and some bad hamstring injuries. But this was unlike any of those.

The pain was unbearable. With past injuries, Smith would be on pain meds for a day or two, then graduate to over-the-counter anti-inflammatories. This time, he took Oxycontin for about 12 days.

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"After surgery, he would just say, 'Give me more,'" Angie says. "He was kind of out of it."

Finally, Smith didn't want to feel so drowsy, so he went cold turkey with the meds.

"The day I stopped, about midday I started to get ornery," Smith says. "I got a headache. It was my body craving the medication. I was having withdrawal symptoms."

He opened the bottle of Oxycontin and dumped the pills in the toilet.

For two months, Smith could not bear weight on his right leg. He got around on a knee scooter initially. Then crutches with a boot. Then one crutch. And there were heel lifts. Each week, he was allowed to peel off a layer of the lift. Eventually, he was left with orthotics.

A father of four, Smith was learning a new meaning of "baby steps."

One week before he was pushing forward despite retching into the weeds, Smith wanted to pack up his gym bag and go home. About halfway through a workout, he turned to Ancheta and said, "Screw this manure." Or something like that.

And he went on. "I'm tired. I can see why guys get to a certain age, they say screw it. I'm not just training to not look fat. I'm training to play in 20 games, to run from other men who are trying to bodyslam me and hurt me. I ain't got to do this. Why am I doing this? I don't have anything to prove to anybody."

His reaction was raw and unfiltered. Smith has rarely been known to hide his feelings.

He started thinking. He has a house in California rented for next offseason. Why wait? He could be on the beach. Toes in the sand.

Smith says he's never had those feelings before. Then again, he's never been 37 before. He's never tried to come back from a torn Achilles before.

So what did he do when he was done venting? Completed the workout.

Smith felt he had been running out of steam before he tore his Achilles. For 216 games, he has competed at a level few could match, throwing around his 5'9" body as if it were covered in armor. Pound for pound, he unquestionably has been one of the NFL's toughest men. "A notorious badass," is how Vikings linebacker Chad Greenway describes him.

Steve Smith Sr. regular-season stats Year Tm Rec Yds TD 2001 CAR 10 154 0 2002 CAR 54 872 3 2003 CAR 88 1,110 7 2004 CAR 6 60 0 2005 CAR 103 1,563 12 2006 CAR 83 1,166 8 2007 CAR 87 1,002 7 2008 CAR 78 1,421 6 2009 CAR 65 982 7 2010 CAR 46 554 2 2011 CAR 79 1,394 7 2012 CAR 73 1,174 4 2013 CAR 64 745 4 2014 BAL 79 1,065 6 2015 BAL 46 670 3 Career 961 13,932 76 pro-football-reference.com

But no man, Smith is learning, has an unlimited supply of fury.

"The Steve Smith Sr. the Baltimore Ravens have is not the same player the Carolina Panthers had," he says.

What he was, Smith will tell you, really doesn't matter now. All that matters is what he is.

He will not delude himself, as most aging athletes do. Smith acknowledges that he's not going to be the same player physically that he was when he was named to five Pro Bowls. But he believes he does have enough athletic juice to keep playing and that his understanding of the game and passion will help him overcome whatever is missing.

Emotion has been a big part of Smith's play, and it has been a big part of his rehab as well.

"When you are young and get hurt, you feel like you can just blow through it," Smith says. "When you are older, you overthink everything, overanalyze. You run the numbers, do the percentages in your head. You start to psych yourself out. You lose the belief in your ability because of your age.

"Age sometimes is more powerful in how we look at things than how we are physically feeling. I realized how negative we can be as we become older. I had to really fight that a lot. I was telling myself, 'I'm too old to come back.' I didn't sleep well."

There were questions. What if I come back only halfway to where I was? How will this affect me long term? Will I be able to play basketball with the kids?

And there were tears.

It was especially difficult before he was ambulatory, when he needed help to do everything—even sitting on a toilet. At times, his wife says, Smith kept to himself and didn't say much about what he was feeling. At other times, he snapped at her when she tried to help him.

Frustration, fear and boredom did not mix well.

"Early on," Angie says, "it seemed like a big mountain to climb."

Smith acknowledges he still has moments of doubt. But he does not fear failing. "I'm playing with house money now, and I ain't got nothing to lose," he says.

To pass the time, Smith watched Netflix. He breezed through three seasons of Gotham. Then there was Daredevil. Video games made the days go by. A little Mad Max, some Madden and FIFA.

Then there was an airplane game he played mostly because his toddler son, Deuce (Stevonne Jr.), enjoyed watching him from his lap while he played it. That gave him joy.

Perspective can be attained in many ways.

"Great work this past week," the email from Ravens trainer Sam Bell begins. "You accomplished a lot in a small amount of time."

Bell outlines goals for Smith and an overall short-term plan. He continues: "I have attached a workout program for the next week and will send you a progression when I hear how you have tolerated the exercises. The exercises have been adjusted minimally, however, the frequency has increased significantly. Use your orthotics in every shoe you wear. … Plan on rehabbing daily with Sunday completely off. … This can be adjusted based on your pain, stiffness or soreness. As usual, if there are any questions, feel free to contact me."

Four attachments outline the exercises Smith should do Monday and Thursday, exercises he should do Tuesday and Friday and exercises he should do Wednesday and Saturday, as well as his daily cardio requirements.

The attachments go into great detail. On the Tuesday/Friday list, there are 25 exercises listed. The number of sets and repetitions for each is specified.

Smith talks of "embracing the grind" of rehab. And this clearly is a grind. Whether he is with his team in Owings Mills, Maryland, back home in Charlotte or even on a business trip somewhere else, Smith is dripping sweat and breathing hard. He also is getting physical therapy, muscle massage and laser treatment to break up scar tissue.

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"At the level he is at, everyone is an elite athlete," Ancheta says. "When you see someone like him push that threshold, you understand why he has lasted and why he has been so successful."

Smith is good at a lot of things. Especially, he is good at surviving. He is quick to tell you he should not be in the NFL today. He's too old. He's too short. He's too volatile. He's too much of a product of his rough upbringing in West Los Angeles.

Seventy-three players were chosen ahead of him in the 2001 draft, 72 of whom are out of the league. He has outlasted all but Drew Brees. Initially, he was supposed to be a return man only—not a wide receiver. He was called injury-prone early in his career. Late in his career, the only team he knew for 13 years fired him.

And now this.

One more thing to overcome.

On the day Smith's stomach objected to the intensity of his workout, Ancheta says he saw some explosiveness in Smith's movements that he had not previously seen.

His Achilles is sore from fatigue, but it isn't painful. It looks like more of a problem than it actually is, as the muscle around the tendon has atrophied considerably. Smith calls the calf on his left leg the "American calf," and the calf on his right "the calf you can feed for 36 cents a day."

As for training camp, he probably will sit out most, if not all, of it. Smith was placed on the physically unable to perform list in late July. What he would love more than anything is to lie in the August weeds and then pounce when the regular season begins. But the day in front of him is the only one that matters now.

"I have the propensity to think about September," Smith says. "But if I do that, I'll go down a path mentally that isn't very good for me."

Smith has come a long way. And he has a long way to go.

Sometimes, where you are going isn't as important as where you are.

Down the stairs of his suburban Charlotte home, Smith walks past the trophy cases. Past the Pro Bowl jersey, the Panthers jersey, the Ravens jersey, the photo of him with former college and pro teammate Jordan Gross, the football he caught for his first NFL touchdown and the ball he caught for his Super Bowl touchdown.

Into the workout room. Smith slips off his shorts. He puts on a pair of special shorts made for an anti-gravity treadmill. Then he steps into the apparatus, zipping himself in. Soon, his lower body is in a bubble, and he is running at a reduced body weight.

The high-tech treadmill was a costly but worthwhile rehab tool for Smith, a way to run in place to get to where he wants to go.

The Ravens were 5-11 last season. Smith feels an obligation to try to help them turn it around. They need him. Head coach John Harbaugh values his leadership, and Smith wants to provide both direction and production for his team.

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And what Smith wants as much as anything is a chance to appreciate the sunset of his career. For most of his football life, he has been too obsessed and focused to appreciate everything around him.

During those days last winter when he was homebound, Smith read a lot. A friend recommended God Never Blinks: 50 Lessons for Life's Little Detours. The author, Regina Brett, shares the story of how it took a diagnosis of breast cancer for her to start enjoying life.

"I was at the point where I was thinking, 'Life sucks,'" Smith says. "When I read it, it gave me perspective. I stopped complaining."

When Smith was a kid in L.A., he rode the bus through the dirty streets in the hood to get to his job at Taco Bell on Pico and Bundy and then to his other job at the Ferris wheel on the Santa Monica Pier. He would occasionally get a glimpse of the Pacific Coast Highway and all the beautiful people in their fancy cars who drove on it. That's where he always wanted to be. Getting there was his overarching goal.

"For me," Smith says, "The PCH is the NFL." He finally made it there in 2001. But it has taken him 16 years to realize the gratification he has felt wasn't from getting there. It was from being there.

It was from taking in the bends and the bridges. The rock formations. Sunsets you could never find in an art gallery. The smell of the ocean. A warm breeze on an arm out the window.

Now, Smith wants to make sure he has time to spend with that rookie who has questions for him. He wants to remember to joke with the guys. He wants to foster relationships. He wants to appreciate this special organization that he is a part of and make it better in ways big and small.

Not long ago Smith was having a conversation with Ravens receivers coach Bobby Engram and teammate Mike Wallace. Engram and Wallace told Smith before he retires, they want to help him get a Super Bowl ring. The Panthers lost in Smith's only Super Bowl appearance in 2004.

Smith's response: "If I win a Super Bowl or don't, life doesn't change. What's more valuable to me is all the blessings I've had, the people who invested in me that I never would have known if I wasn't on this road. So to be honest, f--k that ring. I've gained so many more things doing it this way."

That is not to say playing for a Super Bowl winner wouldn't be the fairy tale. Or winning Comeback Player of the Year wouldn't be awesome. Or making an irrefutable final argument that he is Hall of Fame-worthy wouldn't be fantastic.

But if he never plays another snap in the NFL, well, it's been one hell of a ride.

You might say he could have done without these last nine months. He would say this time has given him a wisdom he will carry with him the rest of his days.

With one leg about half the size of the other, Steve Smith Sr. finally realized this isn't about a destination. It's about a journey.

Dan Pompei covers the NFL for Bleacher Report. Follow him on Twitter at @danpompei.