SAN FRANCISCO — San Francisco strong safety Michael Lewis has sustained his third concussion of the season, going down during the 49ers’ game against Atlanta early in the third quarter trying to tackle Michael Turner.

Lewis, who sustained two concussions during an 11-day span in the preseason, could be sidelined for a prolonged period.
He led with his helmet on the hit Sunday and was face down on the field for several minutes while being examined. He eventually sat up and was helped off the field, appearing dazed. Athletic trainers ran a series of tests on Lewis as he sat on the sideline.
Lewis’ first concussion occurred Aug. 18 during a joint practice with Oakland at the Raiders’ wine country training site in Napa when he got hit by a fullback. He suffered another in an exhibition game at Dallas on Aug. 29, when he fell and took a knee to the helmet.
The 29-year-old Lewis, a Pro Bowl selection in 2004 with Philadelphia, is in his eighth NFL season and third with San Francisco. He ranked third on the team with 118 tackles in 2008.