Brock Purdy

SANTA CLARA, Calif. — Quarterback Brock Purdy will sit out the San Francisco 49ers’ regular-season finale after the team already wrapped up the No. 1 seed in the NFL playoffs.

Coach Kyle Shanahan said Wednesday that Sam Darnold will start in place of Purdy on Sunday against the Los Angeles Rams with nothing at stake for San Francisco (12-4) in the game.

The Niners clinched the No. 1 seed and a first-round bye when they beat Washington last week and Philadelphia lost to Arizona. San Francisco will play its first playoff game at home in the divisional round on Jan. 20 or 21.

Shanahan said he hasn’t decided how much to use other key starters in Sunday’s game, having only decided on Purdy. Shanahan said Purdy and Darnold will split practice time Wednesday, with Darnold getting the bulk of the work with the first team on Thursday.

“I want our team to treat this week as Brock going down on the first play of the game,” Shanahan said. “That’s why I want both repping. I want Brock to get some work this week.”

Purdy finishes his first full regular season as starter with impressive statistics after coming back from offseason elbow surgery. He set the franchise record for yards passing with 4,280 — two more than Jeff Garcia had for San Francisco in 2000 — and leads the league with a 113 passer rating and 9.6 yards per attempt. Purdy also has thrown 31 TD passes.

Darnold gets his first start of the season for the Niners and an opportunity to show off for potential teams next season.

The No. 3 overall pick of the New York Jets in 2018, Darnold signed a one-year contract as a free agent with San Francisco to try to resurrect his career.

Darnold is 12 for 20 for 108 yards, one TD and one interception in brief action this season for San Francisco. His 78.1 career passer rating is the lowest among the 39 quarterback with at least 1,000 attempts since he entered the league.

Shanahan said it will be tough to sit many other healthy players because several players will need the week off to nurse injuries, including starting running back Christian McCaffrey.

McCaffrey left last week’s game with a strained calf and will sit out this week to be safe.

“I’ve played through worse,” he said. “Right now, the situation we’re in, precaution is probably better. … It was more of a cautionary situation and being smart about it than doing something stupid.”

Other players dealing with injuries this week are defensive tackle Arik Armstead (foot), cornerback Ambry Thomas (hand), guard Jon Feliciano (back), safety Tashaun Gipson (quadriceps), safety Ji’Ayir Brown (knee) and tight end Ross Dwelley (ankle).

Running back Elijah Mitchell missed practice with an illness and receiver Jauan Jennings and offensive lineman Jaylon Moore were limited as they remain in the concussion protocol.

Shanahan is hopeful all of those players will be ready for the postseason.