James Cook is running the football about as well as anyone in the NFL.
Buffalo Bills head coach Joe Brady has made it clear that won't matter if Cook can't hold onto it.
Cook has fumbled four times through five games, including twice Monday night against the Los Angeles Rams, prompting media questions directed at Brady regarding Cook's ball security in each of his three media availabilities since Buffalo's 37-34 overtime victory.
By Tuesday, Brady delivered his strongest warning yet.
"It's got to improve or the carries are going to decrease," Brady said.
That's transparency even though Cook is the reigning NFL rushing champion.
Cook led the league with 1,621 rushing yards last season and hasn't slowed down much in 2026. He ranks third in the NFL with 532 yards through five games, is averaging 5.6 yards per carry and has already rushed for more than 100 yards three times.
He ran 25 times for 111 yards and two touchdowns against the Rams.
FUMBLE 🚨Nate Landman punches it out and Aaron Donald recovers!@BUFvsLAR on ESPN
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He also put the ball on the ground twice.
"I don't want James running anymore timid," Brady said Wednesday. "He is playing outstanding in terms of how he is running the football right now. I don't know if anybody is running the ball better than him in the NFL.
"But we're putting the ball on the ground, right?"
That's the problem Buffalo has been trying to solve without taking away what makes Cook so effective.
James Cook fumbles nearly cost Bills against Rams
Cook's most damaging fumble Monday came at about the worst possible time.
Buffalo got the ball first in overtime and Josh Allen immediately connected with Khalil Shakir for 57 yards to the Los Angeles 22-yard line.
On the next play, Cook fumbled.
Rams linebacker Nate Landman punched the ball loose for the second time in the game and Aaron Donald recovered it, abruptly turning what appeared to be a potential game-winning Bills drive into a chance for Los Angeles to win.
The Rams moved into field-goal range before Greg Rousseau blocked Harrison Mevis' 48-yard attempt.
Buffalo got another chance and Tyler Bass kicked a 45-yard field goal to win it.
No one looked as relieved on the field as Cook. The ending prevented his turnover from becoming the defining play of the game.
Brady doesn't want the victory to obscure what happened.
"Don't confuse the quality of the result for if we're doing things correctly," Brady said Monday night. "A lot for us to obviously clean up."
JAMES COOK FUMBLE pic.twitter.com/SUm1SgaO9h
— wok (@wokdior) October 13, 2026
Cook felt much the same way afterward.
"Very disappointed," Cook said. "It could've just changed the game. Just got to hold onto it, just work on it each and every day."
Cook said winning is "everything" to him and he took responsibility for the mistakes.
"Just got to take more care of the ball, hold myself accountable," Cook said. "Just keep moving. Never stay out of the game. The team needs me, never get down on yourself. It's life. It's football. Things happen. So just keep moving."
James Cook has 11 fumbles since start of last season
Cook's fumbles on Monday weren't an isolated problem.
He has fumbled 11 times since the beginning of last season, 10 during the regular season and once in the playoffs.
His six regular-season fumbles in 2025 were the most by any NFL non-quarterback. No other running back had more than four.
Cook already has four this season. He and New York Giants running back Cam Skattebo are the only non-quarterbacks with that many.
Broncos ball! Alex Singleton forces the fumble 😳
— NFL (@NFL) January 17, 2026
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The postseason fumble last season was costly, too.
Cook lost the ball during the first quarter of Buffalo's overtime loss to Denver in last January's AFC divisional round, and the Broncos turned the extra possession into a touchdown.
That's why Brady's concern extends beyond what happened Monday.
"Right now, we're putting the ball in harm's way," Brady said Tuesday. "We know the way that we lose football games is we turn the ball over, right?"
Brady pointed out that Buffalo's two biggest offensive stars both committed turnovers against Los Angeles. Allen threw an interception and Cook fumbled.
"Our two best players turned the ball over last night," Brady said. "James put the ball on the ground. Look, he's doing so many good things running the football. And I don't want to lose sight of how great he's running the ball right now, but we're putting the ball on the ground and it's negating all the positive."
Will Bills reduce James Cook's carries?
Not yet.
Brady showed that against the Rams.
Even after Cook's overtime fumble, Brady said he told the running back he was going to continue trusting him.
"It's not, 'Hey, you fumbled and you don't play,'" Brady said. "But we have to clean these up."
Cook finished with 26 touches Monday and remained central to Buffalo's offense.
Brady reiterated Wednesday that he has no plans to suddenly stop feeding his star ball-carrier.
"I don't want you guys to think that I'm going to stop giving James Cook the ball either," Brady said. "Like I said, he's playing really good football, but that element allows it to not be absolutely great football."
The Bills are trying to address the issue during practice.
Brady mentioned emphasizing "double in trouble" — securing the ball with two hands in traffic — and said Buffalo's scout-team defenders need to make a greater effort to attack the football during practice so Cook has to protect it under more realistic conditions.
"He's aware of it, we're going to continue coaching it," Brady said. "But I don't want him feeling like he has to be scared of how he's running and now he's not hitting the hole."
That's the balancing act.
Cook has become one of the NFL's most productive running backs by running aggressively. Buffalo doesn't want fixing one problem to create another.
But Brady has now made clear where the line is.
"I have all the confidence in him," Brady said Tuesday. "That's why I put him right back out there. But obviously at some point there has to be consequences."
This article originally appeared on Rochester Democrat and Chronicle: Bills say NFL rushing champion could lose carries if fumbles continue