Arizona RB Grigsby sprains ankle at practice

Posted by ESPN.com's Ted Miller

Arizona running back Nic Grigsby left practice Friday on crutches after spraining his ankle, according to Ryan Finley of the Arizona Daily Star. It's unclear how severe the sprain is.

Grigsby rushed for 1,153 yards and 13 touchdowns a year ago and is one of five running backs in the Pac-10 who eclipsed the 1,000-yard mark in 2008.

His backup, Keola Antolin, is very capable. He rushed for 525 yards and 10 touchdowns, including a breakout performance against California when he rushed for 149 yards and three touchdowns.

Greg Nwoko, a 220-pound redshirt freshman is listed No. 3 on the depth chart.