SANTA CLARA, Calif. _ Thad Lewis, who served as the 49ers' No. 2 passer in Sunday's preseason loss to the Texans, tore his ACL on a third-quarter run and is out for the season.
Lewis appeared to suffer the injury on a one-yard scramble. He came off the field following the third-down play and was examined by trainers. Chip Kelly said the 49ers likely would have inserted rookie Jeff Driskel into the game around that time anyway.
Lewis was 12-21 for a team-high 97 yards in the game. He suffered the 49ers only sack and ran four times for 10 yards.
"Again I felt kind of like Blaine (Gabbert), I thought it was a little up and down," Kelly said of Lewis' performance. "I thought some things we really liked out of Thad that he did and then there are a couple others I think he wants back too. I think there are some positives to build on from it though."
Lewis engineered a 12-play drive in the second quarter that ended when running back DuJuan Harris fumbled at the 2-yard line. After the game, Lewis did not suspect he was dealing with a torn ACL. He thought the issue was with his left leg.
"I think we did great, man," he said. "We did awesome moving the ball down the field. Unfortunately, we had that fumble down there. Just like coach told us, you can't win games when you lose the turnover battle. When you get down there you have to score. We did a good job with that. There are a bunch of things we have to clean up. It's the small things. If we do that, we should be fine."
Lewis is the only 49er with experience in Kelly's offensive system, having played with the Eagles last year. He also played under Texans head coach Bill O'Brien at Duke University.
His injury makes Driskel, a sixth-round pick, the de facto third quarterback behind Gabbert and Colin Kaepernick, who is dealing with a sore shoulder and who did not play Sunday.
Driskel completed just four of 12 throws for 20 yards Sunday but ran for 61 yards.
