Wisconsin defensive end Erasmus James, who leads the nation's second-ranked defense, will miss Saturday's game against Northwestern with an ankle injury.
James was injured in the seventh-ranked Badgers' win over Purdue when a tight end "blew his ankle out when he rolled up on him," Wisconsin coach Barry Alvarez said Sunday.
He will be replaced by sophomore Joe Monty.
James leads the Big Ten in sacks, is second in the conference in tackles for loss with 10 and has been the key in Wisconsin's defense becoming one of the nation's best. The Badgers rank second in total defense, first in scoring defense, eighth in rushing defense and fourth in passing defense.
"We have an off week after (the Northwestern game). He takes this game off and we'll try to get by without him," Alvarez said.
Defensive end Jonathan Welch, who also left the Purdue game with ankle injury, is expected to play against the Wildcats.