Yeah, yeah, we know. Next man up.

But … at some point the next man up is simply not capable of doing the job, especially when the next man up is replacing the other guy who was already replacing the main guy.

A look at the snap counts for the Giants in the defensive backfield in Sunday’s 31-18 bludgeoning by the Lions — yes, this was a physical pummeling — shows just how sticky of a situation this is for the defense and the entire wellbeing of the team. It shows that Julian Love stands alone.

Love played all 67 snaps on defense. In the recent past, he was joined by the other starting safety, Xavier McKinney, and cornerback Adoree’ Jackson as 100-percent snap guys. Not anymore. McKinney is out for the foreseeable future after that terrible all-terrain vehicle accident left him with broken fingers and Jackson went down in this game with a knee injury while returning a punt, which was so preventable.

What this all means is defensive coordinator Wink Martindale is going to have to go the situational football route on virtually every snap on defense, which is no way to run a defense. When Fabian Moreau, the other starting corner, went out with an injury to his ribs, Martindale was forced to use rookie Cor’Dale Flott, recently-activated Rodarius Williams and Nick McCloud at the cornerback spots. This is going to be a big issue moving forward, not only against the Cowboys on Thanksgiving — Dak Prescott was slinging it around like a maestro in an impressive rout of the Vikings — but against any capable quarterback moving forward. With four consecutive NFC East games and Prescott, Jalen Hurts and, yes, Taylor Heinicke on deck, the Giants will not have enough capable cornerbacks and safeties to get the job done on any sort of consistent basis.

“For us, that’s what this whole season has been about,’’ Jackson said. “Understand that even when you get all of these reps in OTAs or in camp, make sure everybody is on the same page. And when we bring new people in, make sure they are all of one accord. Next man up mentality. Just have to be ready. Regardless of the situation, what may play out. Just keep fighting, keep battling and don’t let the level of play drop.’’

That can work when the need to mix-and-match is isolated on one player here or there. This is an epidemic. There is an unadulterated truth that players get hurt. If Jackson went down while on the field at cornerback, so be it. He plays every snap and has to run and cover and come up and hit and tackle. It is a violent game and injuries are everywhere. That Jackson was on the field at the punt returner early in the second quarter was not a shock to the system, considering he was used in that capacity a week earlier against the Texans. This move was made at the bye week, after Richie James muffed two punts in the loss in Seattle.

Putting a key player into a special teams role is a risk. Coach Brian Daboll was asked about this in real time the past few weeks and publicly minimized the risk involved here, saying his decisions are all based on what is best for the team. Still, this was a strange one. True, Jackson does have punt return ability on his resume from his time in college at USC and earlier in his NFL career with the Titans. It is not as if he was ever Devin Hester or Deion Sanders back there, though. And it is not as if Jackson was instructed to call for a fair catch whenever the ball sailed his way. He was injured trying to find some running room on a return that went for only three yards and he got hit and tangled with safety C.J. Moore.

Jackson said his knee hyperextended.

“That’s all it was,’’ he said. “It was one of those things. I tried to make a juke, thought it was good, he came down low. Leg was just in the ground. He got me that way. Nothing crazy like that. We were just out there playing ball.’’

Most likely, this is a sprain to the medial collateral ligament and that means Jackson is out 4-6 weeks. He is irreplaceable on the backend of the defense, far and away the top cornerback on the team.

“Yeah, it’s tough,’’ Love said. “That’s our guy, he’s been playing at a high level. To see him go down, that’s very tough. For the game, we need young guys to step up and throw them in the fire, which is a tough thing for any team to do.

“We got to find a way right now. Some young guys have to step up, which I know they’re going to do. Thankfully, it’s a short week because we can get right back in action – that’s my mindset for it.’’

It’s the right mindset to have, but reality is lurking around the corner. The next man up is not nearly as talented as Jackson, who got hurt doing something he probably should not have been assigned to do.

 More that came out of the most complete loss all season for the Giants:

— Losing rookie wide receiver Wan’Dale Robinson for the remainder of the season to a torn ACL is incredibly damaging, for the player and the team. Robinson was enduring typical first-year growing pains, having difficulty staying on the field with hamstring issues and experiencing low production as he tried to find his place in the offense. The front office and coaching staff was taken with Robinson’s quickness and playmaking ability at Kentucky, which is why they selected him with the 43rd overall pick in the 2022 NFL Draft. That quickness and playmaking ability was rarely on display as Robinson fought to get healthy. It was evident in his Sunday’s game, when he caught nine passes for 100 yards, finally showing what all the fuss was about. Then he went down, and out. His development gets halted as he heads to surgery and a lengthy rehab. It is a tough break for the player and a gut-punch to a team that is 7-3 and looking to make a playoff push with a severely-depleted and lackluster group of receivers.

— Defense is more than preventing points. It is also about shaking things up and creating mayhem. The Giants are not great at that. For the second time this season, the Giants failed to get a sack or force a turnover on defense. They are 0-2 in such games, losing to the Cowboys and Lions.

— Empty numbers: The Giants had 413 total yards and 25 first downs against the Lions, both their second-highest totals of the season (they had 436 and 25 in Jacksonville). The Giants were in comeback mode the entire second half, inflating their offensive production.

— The more Daniel Jones throws, the more he loses. His 44 passing attempts against the Lions were the third-highest total of his career. He had 51 pass attempts last season vs. the Rams, and lost. He had 47 throws against the Eagles late in the 2019 season, and lost.

— When Jon Feliciano went out with a neck injury, Nick Gates moved in at center, finishing up the game and playing 25 snaps. That was the heaviest workload for him since his return from his fractured leg ordeal. Gates played a total of 18 snaps in his two previous games, all as an extra blocker on the offensive line. If Feliciano is not ready to play on Thursday, can Gates handle a full load in Dallas?

— The last time Graham Gano missed two extra points in one game? Never. This was a first for Gano in his 184th career game. His first PAT against the Lions was blocked. The last time a Giants kicker missed two extra points in a game came exactly six years earlier, when Robbie Gould did it in a 22-16 victory over the Bears in 2016.

— There is design and there is necessity. They came together to produce 33 offensive snaps for former forgotten man Kenny Golladay. With Robinson forced out with a knee injury, Golladay logged more time on the field. He was targeted twice and caught two passes for 29 yards. He is being used on in-cuts and slants to take advantage of his size, acknowledging that he is not running away from anyone. It is better than nothing.