San Francisco 49ers All-Pro linebacker Patrick Willis will have an MRI on Tuesday to determine the severity of the toe injury he suffered during Monday night's game against the St. Louis Rams, sources told ESPN NFL Insider Ed Werder. Willis, who left the locker room wearing a walking boot on his left foot, said after the game that X-rays were taken but he was not sure of the severity of the injury. "We'll find out more [Tuesday]," Willis said as he limped to the team bus after the 49ers' 31-17 victory against the Rams. He left the game in the second quarter and did not return. Willis believes the injury happened when he jammed his foot into the artificial turf while chasing a Rams running back. He was replaced by rookie Chris Borland. ESPN