TORONTO — The Bills placed rookie defensive end Chris Ellis on season-ending injured reserve today because of an ankle injury.

The third-round draft pick out of Virginia Tech had played the past seven games, making seven tackles. It's not clear whether he was hurt in a 10-3 loss to San Francisco last weekend, but the injury kept him from practicing this week as the Bills (6-6) prepared to host the Miami Dolphins (7-5) at Toronto on Sunday.

The Bills didn't provide details on the severity of the injury.

Buffalo activated Corey Mace from the practice squad, giving the Canadian-born defensive lineman an opportunity to make his NFL debut in his native country in the first of the Bills' five annual regular-season games in Toronto.

Signed by the Bills last year as an undrafted free agent out of Wyoming, Mace spent all but one week on the team's practice squad last season and the first 13 weeks this year.