49ers down to two healthy QBs after Lewis tears ACL

Less than a week after the 49ers had four quarterbacks throwing in practice, that number will probably be reduced by half when they gather for Tuesday’s workout.

On Monday, the 49ers learned Thad Lewis had torn an ACL in Sunday’s preseason loss to the Texans and will be out for the season.

On Monday, head coach Chip Kelly said he’d just learned of Lewis’ injury before meeting with the media and hadn’t had a chance to discuss signing another quarterback with general manager Trent Baalke.

After being tackled, he limped off the field and didn’t return, having completed 12 of 21 passes for 97 yards in six series against the Texans.

Driskel, the No. 207 overall pick, completed 4 of 12 passes for 20 yards and missed several open receivers in his debut Sunday.

Last year, six NFL teams were forced to start at least three quarterbacks.

“Injuries are part of the game, but you hate to lose a guy like that who has had experience and been in the system,” said quarterbacks coach Ryan Day, who was Lewis’ position coach with the Eagles last year.