Fall off the horse, get right back on.

That’s the advice Giants running backs coach Craig Johnson has for rookie Wayne Gallman.

With the Giants’ season going nowhere, the team is looking toward the future. So guys such as Gallman are receiving auditions. After three inactive weeks, Gallman has played five straight games but last Sunday against the Rams, Gallman had a critical fumble, one of about 219 awful Giants plays in the 51-17 debacle.

“What I told him when he came off the field is there is no excuse ever in my mind for a back ever to turn the ball over,” Johnson said of the former Clemson back. “I refuse to accept that. That being said, when it happens, you can’t change the past, but you can go forward. So what I’ll tell him is, ‘You know what? Don’t dwell on it, move on, trust yourself, trust your fundamentals, but understand that ball security is a really critical element. But when you’re on the field, you got to play.’ I don’t want any player being timid and being scared about playing with a football. They got to make sure they protect it and go on and help us win.”

Defensive end Olivier Vernon (ankle) is listed as questionable, but he hopes to return after missing four games — the first time in his career he sat out.

“I’m feeling great man so we’ll see how it goes on Sunday,” said the sixth-season veteran Vernon, who is “making progress,” according to coach Ben McAdoo.

“I’m taking it day-by-day,” Vernon said. “We got practice tomorrow so we’ll see how that goes and look forward from there. … You never want to be on the outside looking in when all of your brothers are out there playing. But it was out of my control, nothing I can do about it. All I could do is just get healthy and now I’m back.”

And it has been weird watching.

“I was thinking the other day, some of the guys in the building, some of the former Giant players that have been in here and I could see from their point of view, their perspective that dang, if they could just play another game,” Vernon said. “In my mind, I was like, ‘Dang, is this how it feels to not play?’ And it felt weird. I’m just glad and I’m fortunate that it wasn’t worse than what it could have been. I’m just glad to be back and enjoy my time and enjoy my teammates.”

Linebackers B.J. Goodson (ankle), Devon Kennard (quad) and Keenan Robinson (quad) officially are out for Sunday. Cornerback Donte Deayon (ankle) is listed as doubtful. Linebackers Jonathan Casillas (neck) and Calvin Munson (quad), and defensive end Kerry Wynn (knee) all are questionable.

Linebacker Kelvin Sheppard, who played in every game, starting 11, last year for the Giants came back to the team Tuesday — he was released in September by the Bears. So his familiarity with the system should help with all the injuries.

“He’s going to have an opportunity to play,” McAdoo said in a press gathering Friday.

Earlier, McAdoo told the team’s website that Sheppard brings far more than knowledge of the system.

“Obviously it’s a challenge to come in, in the middle of the season, even though he has knowledge of our systems and the way we do things, and has been here in the past,” McAdoo said. “But he’s a unique individual in a lot of ways. He’s got leadership capabilities, he has some charisma, he gets football and he brings some positive energy. So it’s interesting to see.”

Calvin Munson and Curtis Grant may wind up starting Sunday, given the Giants’ injury situation. Munson had two earlier starts this season.

McAdoo, on the team’s website, praised the effort he has gotten from the two undrafted guys.

“I told [Munson] that he would have a golden opportunity here. … Not only has he taken advantage of it, but he’s taken it and he’s running with it,” McAdoo said. “He’s a throwback type. He’s a tough guy. He can handle multiple jobs on [special] teams and at the linebacker position. He gives you everything he’s got. He’s a tough guy, I’m glad we have him.”

McAdoo also gave props to Grant for “how hard he worked at learning the defense and studying it and being able to play multiple spots. … He plays with a lot of physicality on special teams. That’s something that I appreciate and he’s really growing into a good, hard-nosed player.”