James Cook was lined up for a prominent role in Buffalo's offense as the season started.

He hit a speed bump early Thursday.

The rookie running back got the call in the first quarter during the Bills' season-opener against the Los Angeles Rams. He took a handoff from Josh Allen, ran right off tackle and promptly fumbled after a 2-yard gain.

Fortunately for the Bills, they got the ball back in short order after Matthew Stafford threw an interception to cornerback Dane Jackson. That didn't matter much for Cook.

The quickest path for a running back to the bench is by fumbling — especially for an unproven rookie. He didn't touch the ball again in Buffalo's 31-10 win.

Cook starred at Georgia as a dual threat out of the backfield. He tallied 728 yards on 6.4 yards per carry and caught 27 passes for 284 yards while scoring 11 total touchdowns as the Bulldogs won the national championship last season. His athleticism and versatility as a pass-catcher made him a second-round pick (63rd overall) in April's draft.

With a role in Buffalo's anticipated high-octane offense, he was likewise a popular sleeper pick in fantasy drafts. After Thursday's early fumble, that sleeper potential may have to wait. The Bills have veteran options at running back, led by Devin Singletary and Zack Moss. Cook's path to carries — and fantasy relevance — could very well be on pause.