Ultimately, head coaches are judged by wins and losses. In Rex Ryan's case, there's one loss he absolutely can't afford.
The locker room.
Ryan used his mulligan after last season, famously admitting he "lost the pulse" of his team. The New York Jets coach has done an admirable job of keeping the team together through its worst stretch of football since 2007, but the Mark Sanchez-Tim Tebow controversy could threaten team harmony.
If Ryan decides at some point to make the quarterback change, he could have a mutiny because you get the distinct feeling that it's still a pro-Sanchez locker room.
"There's no other viable option," one player told ESPNNewYork.com, speaking on the condition of anonymity.
That, of course, is a direct shot at Tebow, who has had more than three months to convince his new teammates he can be The Next Guy. He apparently hasn't done that. He certainly hasn't convinced Ryan, who would've made the change during the bye week if he thought Tebow could rescue the season.
If Ryan went to Tebow, it would be akin to waving the white flag -- at least that's how it likely would be perceived in certain segments of the locker room.
Maybe that turns in a week. If Sanchez is hopeless Sunday in St. Louis, the way he was hopeless in Seattle, it could change to a nothing-to-lose mentality. At some point, the team will look at Ryan sideways if he keeps sending out an ineffective quarterback.
This is a difficult situation to navigate. To borrow Ryan's phrase, he needs to have the pulse of the team before making a move at the quarterback position. If the season ends in turmoil, it will be an indelible stain on the coach's record.
Ryan applied stain remover after last season's ugly fallout, making a concerted effort to rebuild and strengthen team chemistry. He went so far as to send the players and coaches to a day-long leadership seminar before the start of the season.
If the dysfunction returns, it would be tough to explain his way out of another episode.
"He will lose the locker room [if he benches Sanchez]," Damien Woody, a former Jet turned ESPN analyst, said in a phone interview. "The biggest reason is, the players see what Tim Tebow is on an every-day basis in practice. The players clearly see that Mark is still the better option."
Say this for Ryan: He's a man of his convictions. When the Jets traded for Tebow, and conspiracy theorists claimed Sanchez was on borrowed time, Ryan professed his loyalty to Sanchez, insisting Tebow would be a role player and a backup quarterback.
Do you believe him now? Obviously, Tebow hasn't flourished in that role, mostly because the coaches have struggled to define it.
Ironically, they seemed to have a better, if not complete grasp of Tebow's role in Sunday's loss to the Seattle Seahawks. They used him in two short-yardage situations (one aborted by a penalty) -- the man is a 250-pound runner -- and they let him throw a few bubble screens to Jeremy Kerley.
Then came the head-scratching decision to insert Tebow on a first down from the Seahawks' 48, right after Sanchez threw a 32-yard completion. You didn't need to be fluent in body language to read Sanchez's reaction.
The CBS cameras caught him on the sideline, wearing a look of disgust as he stood next to offensive coordinator Tony Sparano. He threw up his hands, shrugged his shoulders and then put his hands on his hips. After the game, Sanchez revealed a hint of frustration as he explained it to reporters.
"I'd be frustrated, too," Woody said. "You hit a big play, you've got some momentum and you get yanked out. That's just bad coaching."
Sanchez can't be happy with this two-quarterback system -- or whatever you want to call it -- but he takes the high road, knowing that if he cracks, the team cracks. He's a good actor; maybe it's because he grew up near Hollywood.
His former college coach, the Seahawks' Pete Carroll, was pretty chatty Monday on a Seattle radio station, saying he feels bad for Sanchez because he's in a "difficult" and "disruptive" situation. Carroll and Sanchez remain close; you wonder if he was acting as Sanchez's mouthpiece.
Sanchez still has the support of his current coach and his current teammates, including Antonio Cromartie, who said that anybody who believes Sanchez should be benched "can kiss my a--."
Some outsiders think Ryan's loyalty to Sanchez could cost him his job. The same could be said of the alternative. The coach is in a pickle.