Woolfolk's father, Butch, a former Michigan All-American running back, told the Detroit Free Press that Troy sustained a dislocated ankle that had to be reset. There's possible ligament damage and a decision on surgery will be made later.
"[The coaches] said it happened during a tackle. His foot got stuck in the turf and his ankle just turned," Butch Woolfolk told the Free Press. "It was dislocated and when they put it back in the socket, they did an X-ray and found out about the ligament [damage] and the bone broke."
Jim Creech, Troy's high school coach spoke with both Troy and Butch on Tuesday night and told ESPN.com's Joe Schad that "it looks like [Woolfolk will] miss the season" with a dislocated ankle and broken bone in his leg, but could use a medical redshirt and return next season.
Coach Rich Rodriguez said in a statement that Woolfolk was transported to University of Michigan hospital with the team physician. Rodriguez didn't elaborate on the injury, citing medical privacy rights.
A spokeswoman for University of Michigan Health Systems told ESPN.com that Woolfolk was treated in the University Hospital emergency room and released earlier this evening, between 7-8 p.m. ET.
Woolfolk started all 12 games last season, six at both cornerback and safety, and is the most experienced member of the Wolverines' secondary. He recorded 46 tackles and a pass breakup in 2009.
The cornerback position has been hit particularly hard recently at Michigan.
All-Big Ten selection Donovan Warren left a year early for the NFL, and reserve J.T. Turner last week was granted his release from the team. Top recruit Demar Dorsey, a candidate to play corner and safety, was denied admission in June.
Adam Rittenberg covers Big Ten football for ESPN.com. He can be reached at firstname.lastname@example.org.