In the Penguins' run to the Stanley Cup last season, Letang had 15 points (three goals, 12 assists) in 23 games, averaging 28:52 of ice time.

Letang, who has not played since Feb. 21, will need 4-6 months to recover, which could take him into the start of training camp next season. He had 34 points (five goals, 29 assists) in 41 games this season.

CRANBERRY, Pa. -- Pittsburgh Penguins defenseman Kris Letang will miss the Stanley Cup Playoffs because of a herniated disk in his neck that will require surgery.

"Right now, it's pretty hard to swallow. It was not expected," Letang said Wednesday. "I was going through rehab. It was going really well. It's just in the last week that it blew up on me. It's hard, but like I've done in the past, I'm going to put my energy into getting better and get back to where I was."

Following an MRI in February, Letang, 29, began skating on his own but experienced plateaus in his recovery.

"Within the last week, he was obviously symptomatic, which spurred more inquiry from our medical staff," Penguins coach Mike Sullivan said. "That's how it evolved."

Video: NHL Tonight on Kris Letang's season-ending injury

It was decided Letang would have a second MRI.

"The [first] MRI revealed that I had a herniated disk, so we took a break and we thought the best treatment for it was to rest and try to get better, and be ready for the playoffs," Letang said. "I was doing well on the ice. I was getting ready and we asked for another MRI to make sure it was good. At that moment, I realized I needed surgery. So, that's where it stands."

Following a 5-1 loss to the Chicago Blackhawks on March 29, Sullivan said he was confident Letang would be available for the start of the playoffs.

"He was making significant progress," Sullivan said. "He was skating. He was on the ice. The next step was he was going to join the team in practice.

"Our doctors, our medical staff felt as though it made the most sense to take a conservative approach without surgery. They were fairly confident that Kris could recover from this in time for the playoffs. We were all very confident that was going to be the case."

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After playing 140 games the previous two seasons, Letang was sidelined from Oct. 18-Nov. 2 with an upper-body injury. He also was placed on injured reserve on Dec. 17 and again on Jan. 16, each time with a lower-body injury, and he missed a combined 11 games.

"[The herniated disk] was an accumulation of events over time," Sullivan said. "It wasn't any one incident when it occurred. Having said that, there was no correlation between his earlier injuries during the year and this particular one."

Letang has experienced several long-term injuries in his 11 NHL seasons. His most significant came in January 2014, when he had a stroke that kept him out six weeks.

"It's obviously disappointing," Sullivan said. "He's an elite player and a great teammate. He's a tough guy to replace. But this team has done it all year long, and that's what we're going to have to continue to do."

The Penguins also are without defensemen Trevor Daley (knee) and Olli Maatta (hand). Daley practiced in a regular contact jersey Wednesday and Maatta joined practice in a yellow no-contact jersey. Sullivan said he is optimistic forward Evgeni Malkin (upper body), who hasn't played since March 15, will be ready for the playoffs.

"We've been missing guys all year," Maatta said. "Our strength is our depth. I think that's something we're confident with."

Without three of its more prominent defensemen, Pittsburgh has relied heavily on Justin Schultz, who has an NHL career-high 49 points (12 goals, 37 assists) in 76 games.

Video: PIT@WPG: Schultz rips a slapper top-shelf for PPG

"[Schultz] is an important guy for us. He has been for quite some time now," Sullivan said. "I don't think he has to assume this great burden of responsibility. I think he has to continue to be the player he's been for us for all season long."

The Penguins are 12-5-3 in their past 20 games without Letang. With the additions of defensemen Ron Hainsey and Mark Streit before the NHL Trade Deadline, Letang said he thinks Pittsburgh could repeat as Stanley Cup champions without him.

"The way we've been battling," Letang said, "take an example like last year when [Evgeni] went down in a crucial time, and I think everybody got closer. We found a way to get up in the standings and win a Cup when Geno came back. I think we can do the same thing. We've got great assets on [defense].

"That team went through so much and they've learned so much. I think they have the experience that we need."