With Garoppolo sidelined at the start of the second half because of a calf injury, Lance led the 49ers' offense for the remainder of Sunday's 28-21 loss against the Seattle Seahawks. He finished the contest 9-of-18 for 157 yards and two touchdowns, and added seven rushes for 41 yards.
As play resumed, Garoppolo, who was initially labeled as questionable to return, was shown on the sideline not wearing a helmet, which all but confirmed the veteran's afternoon was over and Lance's turn to take the reins had officially begun.
Prior to exiting, Jimmy G went 14-of-23 for 165 yards and touchdown. He also threw one interception and took a sack.
"He got hurt sometime in the first half. He said he got stepped on," coach Kyle Shanahan said after the game. "He played for a while with it. We didn't think it was that bad at the time. ... About a minute before halftime he was trying to get it going, but he just couldn't push off it."
Shanahan added that the team is still not sure if Garoppolo suffered a bruise, contusion or strain.
A somber Garoppolo revealed during his media session that the injury occurred in his right calf after the first series and he felt it travel "down the Achilles a little bit." He added that he's "hopeful it will just be a couple of weeks" for him to heal pending the results of Monday's MRI.
"It sucked," he said. "I mean, just in between series, I could feel it tightening up and everything. I thought I could gut it out, tried to for the first half but it's just tough, man. I don't know. Been in this situation too many times, it's getting real old. So, just one of those things that's part of the business."
With the game tied 7-all, the Niners played it conservative on Lance's first series, dialing up three consecutive runs for fellow rookie Trey Sermon which yielded a first down and 21 yards. The drive concluded with a punt after Lance failed to pick up another first down after rushing for a yard on third-and-4.
Seattle punted after a four-play series but Lance was unable to get anything going on his second series. The drive ended following a pair of incomplete passes to George Kittle and Deebo Samuel that bookended a 6-yard Sermon run. The Seahawks followed with consecutive TD drives to take a 21-7 lead.
For his third act, Lance connected with Samuel for just the second completion of his career. The play? A huge 76-yard catch-and-run touchdown late in the third quarter that came after two Sermon runs and a 4-yard QB scamper. San Francisco trailed 21-13 entering the fourth quarter.
After watching the Seattle's lead increase to 15 following a 14-yard Alex Collins TD run, Lance and Co. attempted to mount a furious comeback. In need of two trips to the end zone to have a chance at a victory, the 49ers could only manage one, which came with under a 1:30 remaining on their third fourth-quarter drive. The previous sequences ended in a punt and turnover on downs, respectively. Seattle eventually salted the game with a couple of Russell Wilson kneels.
Despite falling short, the 49ers should be encouraged by Lance's play, especially considering the circumstances. His ability to read defenses will continue to evolve but the 21-year-old showed flashes that demonstrated why the club took him third overall in April.
If Garoppolo's injury lingers into next week, Lance will get a chance to show what he's got in his first NFL start against the undefeated Arizona Cardinals.