49ers safety Antoine Bethea (torn pectoral muscle) placed on IR

The San Francisco 49ers have placed safety Antoine Bethea on the injured reserve with a torn pectoral muscle, according to Matt Barrows of The Sacramento Bee.

In seven games, Bethea had recorded 32 tackles and a sack for San Francisco. Rookie Jaquiski Tartt is expected to make the start in place of Bethea.

The 49ers defense takes a hit with the absence of the three-time Pro Bowler as San Francisco has struggled this year by ranking 20th in points allowed per game and 30th in both passing defense and overall defense.

• The Playbook: A complete guide to Week 7 action around the NFL

The team has activated Jerome Simpson, who missed the first six games of the year after being arrested in July 2014 on a misdemeanor charge for having marijuana and an open bottle of alcohol in his car while driving with a restricted license. The incident marked his third arrest. He did not play last season.

- Christopher Chavez