Thumbs crossed

49ers playoff fate depends on quarterback situation

SANTA CLARA — The playoff scenario for the San Francisco 49ers is pretty simple — a Week 18 win against the Rams or a loss by New Orleans will send the Niners to the postseason for the second time in five seasons under coach Kyle Shanahan.

The more complicated question is who will San Francisco start at quarterback for the crucial season finale.

Rookie Trey Lance fared well in his second career start on Sunday, throwing two TD passes in place of an injured Jimmy Garoppolo in a 23-7 win over the Houston Texans that set the stage for the final game.

Garoppolo injured his right thumb the previous week in a loss at Tennessee and was unable to throw a football at all last week for the 49ers (9-7).

Coach Kyle Shanahan said Monday that he hopes the time off for Garoppolo will give the injured ligament in his thumb more time to “re-latch” but is unlikely to be completely healed, leading to what could be a difficult decision.

“If Jimmy’s 100% healthy and could do everything, like perfect, then I would definitely go with Jimmy,” Shanahan said. “I’m not just going to throw a guy in after one game like this, when Jimmy’s been doing it for us all year. I think it’s going to be hard for Jimmy to be 100%, which is how most people are right now at this time of year. But Trey did a good job, if Jimmy can’t go, we won’t hesitate at all. But if we feel Jimmy can go and play confident, then Jimmy will be out there.”

Garoppolo struggled throwing the ball after hurting his thumb against the Titans, but will try to return to practice on Wednesday.

Lance overcame a slow start and early interception to go 16 for 23 for 249 yards and two touchdowns against the Texans.