SANTA CLARA — Trey Lance did not emerge unscathed from his 49ers' starting debut, a 16-carry workload that left him with a sprained left knee.
An MRI on Monday revealed that Lance did not sustain a long-term injury but one that could require one to two weeks of recovery.
The 49ers (2-3) have their bye this week before hosting the Indianapolis Colts on Oct. 24, all of which puts in question whether Lance or Jimmy Garoppolo will be healthy enough to start at quarterback.
Shanahan said the hope is for Garoppolo to return from a calf injury that sidelined him the past 1 1/2 games.
As for Lance, the rookie dual-threat artist was not sure which play resulted in his knee injury during Sunday's 17-10 loss at Arizona, and it's something he didn't feel until he got in bed Sunday night, Shanahan said.
"It should be a one-to-two-week thing, but possibly just one," Shanahan said on a media conference call, noting that Lance will be re-evaluated later this week and won't know until next week if he has a chance to face the Colts.
Shanahan said he joked with both quarterbacks that they'll keep each other company rehabilitating at the team facility during the bye week. If neither is capable of playing against the Colts, the 49ers would summon Nate Sudfeld, who reverted to the practice squad Monday after suiting up as Lance's backup Sunday.
Shanahan has maintained that Garoppolo is the 49ers' starting quarterback, when healthy, and nothing has changed "big picture" on that.
Neither are healthy, so that tables a quarterback controversy, right?
"He gave us a very good chance to win that game and I know he will give us a chance to win a lot going forward," Shanahan said of Lance. "But it's more of a decision than 'what player do you want to go with.'
"There's a whole team here. There's a lot more that goes into it. These three losses we've had in a row, the answer, good or bad, is not just the quarterback. We have to play better all around."
Lance passed for 192 yards (15-of-29, one interception, two sacks) but it was his 89 rushing yards on 16 carries that created the most buzz, if only because of it being the most runs by a 49ers' quarterback since Colin Kaepernick's 16 carries for 181 yards in a January 2013 playoff win over the Green Bay Packers.
"I was proud of him," Shanahan said. "He went into a tough environment vs. a real good team. He did a lot of real good things. He threw a bad pick on that first drive but bounced back well.
"He was aggressive in what he saw. When he saw it right, he let it rip. When he didn't think something was there, he ran aggressively. He did a real good job through it all. It was a good first experience for him."
Lance's biggest collision came just short of the goal line when he was stopped short by a pair of defenders, one of whom, Isaiah Simmons, left with a concussion.
On the play, Lance initially was supposed to throw to Elijah Mitchell out of the backfield, but the defense changed that plan, and even though it appeared Ross Dwelley and Kyle Juszczyk were open for a short toss across the middle, Shanahan agreed with a reporter's contention that it was "Monday morning quarterbacking."
Still, 16 carries? At least one too many, considering his injury.
"Yeah, there's a couple times where you could have got a completion down the field instead of running, but there weren't any that were drastically the wrong decision," Shanahan said.
"Even the one he threw a pick on, he could have ran for probably 15 yards, but the guy he saw, he saw it right and (Travis Benjamin) was open, so decided to throw it instead and try to get the 15 yards through the air. It could have gone either way. The ball just sailed on him."
Since Shanahan's arrival in 2017, the 49ers have used three quarterbacks in every season but their 2019 run to the Super Bowl.
Sudfeld, a 6-foot-6 Modesto native, has 37 career pass attempts (one touchdown) from the previous four years on the Philadelphia Eagles.
"I'm pumped to have Nate here," Shanahan said. "He was ready to go yesterday. He's been ready to go every week. He's as big of a pro as it gets, so if his number is called vs. Indy, I know he'll be ready."
— The 49ers' failed fourth-down results had Shanahan somewhat second-guessing things Monday: "When you look back and you're 1-of-5 on fourth down, that's something like, 'Damn, obviously I shouldn't have (gone for it) if we only got 1-of-5. But every single one of those, I was confident in the decision."
— Linebacker Marcell Harris sustained a right-thumb fracture that will require surgery Tuesday, but he is not expected to miss an extended time.
— JaMycal Hasty (ankle) has a "possible chance" of coming off injured reserve next week, but fellow running back Jeff Wilson Jr. likely will remain out until late November because of his meniscus surgery in May, Shanahan said.
— Linebacker Dre Greenlaw (groin) is expected to return a week or two after the bye.
— Wide receiver Jalen Hurd (knee) and safety Tarvarius Moore (Achilles) remain on injury lists with no timeline on a potential return, Shanahan said.
— Right tackle Mike McGlinchey avoided an ankle injury after Lance barrelled into him on an early run.
— Cornerback Davontae Harris was activated off injured reserve.
— Cornerback Buster Skrine's contract was terminated.
— In addition to Sudfield, tight end Tanner Hudson also reverted to the practice squad.
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