The NCAA's career rushing leader injured a knee while practicing in training camp with the New York Jets on Friday, and the team placed him on the waived-injured list the next day.
"Nothing certain, but I'd say it's not looking good for him to be back anytime soon," said coach Eric Mangini, who normally doesn't divulge even the most minimal of injury information.
When asked if it was the left knee - which Woodhead appeared to be favoring after the injury - Mangini said: "I think it was." A team spokesperson later confirmed the injury was to Woodhead's left knee.
The exact nature and severity of the injury wasn't immediately known.
"Danny's a positive guy," agent Dan Hoven said. "I'm sure that he's going to make something positive out of this injury."
The stocky 5-foot-7 running back, a rookie free agent from Chadron State who was already an early training camp fan favorite, went down after running the ball during 11-on-11 drills and pointed to his knee before being helped to the sideline by running back Thomas Jones, fullback Tony Richardson and a team trainer.
He was attended to in a small tent on the sideline, and, after several minutes, Woodhead was carted from the field and into the team's facility.
The native of North Platte, Neb., was undrafted - mostly because of his size - despite rushing for 7,962 yards in four seasons at Chadron State. Woodhead also compiled 9,479 career all-purpose yards, second-best in college football history, and was a two-time Harlon Hill Trophy winner as the nation's top Division II player.