SANTA CLARA, Calif. — No George Kittle? No Trent Williams?

On Sunday, their absences were no problem for a San Francisco 49ers offense that piled up a season-high 498 yards, gained 32 first downs and had — by far — its longest run of the season.

That 41-yarder in the first quarter by Christian McCaffrey went to the left side of the offensive line. That’s where the 49ers were without Pro Bowler Williams, who was limping on the sideline with a hamstring strain, for all but one snap. When he left the game, little-known Austen Pleasants, who had played 12 offensive snaps this season, all of them in garbage time, went in.

And the offense didn’t skip a beat in a 42-38 win.

“To have him play the whole game and for it not to be an issue? I mean, I only talked about him on one third-down (play),” 49ers coach Kyle Shanahan said. “My sense is that he played real good.”

A big-time performance by an unfamiliar player has been a theme for this year’s 49ers.

When Kittle missed five games early in the season, for example, tight end Jake Tonges stepped forward and caught three touchdowns, including the game winner in Seattle in Week 1.

Sunday evening was an encore performance for Tonges. He caught seven of the nine passes that went in his direction, including San Francisco’s first touchdown. With the ball at the 1-yard line, the 49ers sent in all three of their healthy tight ends — Tonges, Luke Farrell and Brayden Willis — signaling they’d plow forward with a run. Instead, quarterback Brock Purdy rolled out and found Tonges alone in the end zone, foreshadowing how discombobulated the quick-footed Purdy and the offense would make the Chicago Bears look the rest of the night.

One area in which the backup-heavy 49ers struggled early in the season was the run game. McCaffrey averaged fewer than three yards per carry through the first few weeks and couldn’t break any big gains. The offense had to lean on him as a pass catcher, not as a runner.

That lack of production was attributed, at least in part, to Kittle’s absence. So when the team found itself without Kittle and Williams, who was hurt while trying to run down Bears linebacker T.J. Edwards after a first-snap pick six, it seemed as if San Francisco’s running game would suffer.

It didn’t.

McCaffrey finished with a season-high 140 yards and a touchdown while Purdy added 28 yards and two rushing touchdowns.

Pleasants, who had bounced among various teams’ practice squads since 2020, was the point man on a lot of those runs. In fact, if you had tuned in late and missed Williams’ exit, you might not know he was missing.

The 49ers signed Pleasants to their practice squad last Dec. 17, when injuries struck their offensive line. He played extensively in late-season losses to the Detroit Lions and Arizona Cardinals and caught offensive line coach Chris Foerster’s eye in the process.