NFL

Giants’ O-line quickly becoming ‘Oh no’ line as Mosley goes down

After starting left guard Geoff Schwartz went down — possibly for the season — the mantra coming from Giants practice Sunday was next man up. But whoever that next man is — likely Weston Richburg — with the way Big Blue’s line already has been struggling, the situation at guard could go from a nuisance to a nightmare.

Schwartz got a four-year, $16.8 million deal this offseason to help shore up last year’s shaky line, but the unit has struggled in preseason. With his toe injury to be re-examined this week and potentially costing him six-to-10 weeks — and starter Brandon Mosley leaving practice Sunday with a tight back — others will be forced to step in. But will they be able to step up?

Richburg got first-team reps in Schwartz’s old left-guard spot, with offseason signing John Jerry standing in for Mosley at right guard Sunday. But with Mosley’s sore back not expected to be a long-term issue, Richburg likely will get the nod despite being small (6-foot-3, 298 pounds), green (a rookie) and out of position (a center at Colorado State).

“As an offensive lineman, you have to be ready for something like that. … You have to be ready for any kind of injury or anything like that that happens. I was ready for whatever came at me,’’ Richburg said. “Just minimize mistakes is a big thing, quit making mistakes and if you do just clap it off and continue to play fast. If you’re playing slow, you’re holding back.

“Right now, I’m playing a lot of guard, so I want to get better at guard since that’s something I didn’t do a lot of in college. I just want to keep progressing at that position and continue to get better. … You’re pulling more as a guard. Your pass set is different. It’s a whole different animal, just like tackle is different than guard or center. You just have to get used to it and settle in a little to feel better.’’

The second-round pick was solid in rookie camp and seems to have a grasp of the new offense. He has improved from a poor preseason opener against Buffalo, and on Friday he easily handled playing both guard spots next to center J.D. Walton. If he can handle bigger defensive tackles, he might be a viable option.

“We’ll get out there at practice and iron out all the wrinkles and just make sure we are all on the same page,’’ Walton said. “[Richburg is] doing good, he’s playing well.

“We are in the NFL — it’s the next man up. Everybody is ready to go. We’ve got to be on the same page. … You give [the younger guys] as much help as you can, but it’s their job. Everybody as an offensive line works together to make sure each other knows what each other’s doing.’’

And while running back Rashad Jennings expressed faith in Richburg — “He’s a good, physical lineman. He’s a guy that always wants to finish his blocks. There’s no question that he can get the job done,’’ Jennings said — the job could fall to Jerry, or possibly even Dallas Reynolds, who played late last season.

“It’s the next-man-up mentality,” Jerry said. “I feel really bad for Schwartz. It’s very unfortunate, it’s sad. [But] at the end of the day, its next guy up. The next guy has to go.”

Jerry, 6-5, 340 pounds, comes with a host of question marks, even beyond being implicated in last season’s bullying scandal in Miami. After offseason knee surgery, he missed OTAs and mini-camp, and has struggled in every preseason game. He worked with the first team Sunday, although Tom Coughlin admitted that was largely because of Mosley’s absence.

“He might’ve rotated in some, but that’s the reason he was where he was most of the time,’’ Coughlin said. “[Mosley’s] back tightened up. He came out ready to go, and all of a sudden I saw him over there stretching, and that’s what it was.’’

For his part, Jerry said his knee was fine.

“I’m feeling pretty good about it. If I’m called upon to go play, then I feel that I’m ready to go play,” Jerry said. “But at the end of the day, it is coach’s decision. It’s not up to me.”

Asked if he felt there were still spots up for grabs on the line, he said, “That’s why you’re here, to compete for a job. Jobs are always open.’’