Stanford switches QBs, will start Keller Chryst at Arizona

SEATTLE, WA - SEPTEMBER 30: Quarterback Keller Chryst #10 of the Stanford Cardinal is hit as he throws by linebacker Connor O'Brien #29 of the Washington Huskies on September 30, 2016 at Husky Stadium in Seattle, Washington. (Photo by Otto Greule Jr/Getty Images) less SEATTLE, WA - SEPTEMBER 30: Quarterback Keller Chryst #10 of the Stanford Cardinal is hit as he throws by linebacker Connor O'Brien #29 of the Washington Huskies on September 30, 2016 at Husky Stadium in ... more Photo: Otto Greule Jr, Getty Images Photo: Otto Greule Jr, Getty Images Image 1 of / 8 Caption Close Stanford switches QBs, will start Keller Chryst at Arizona 1 / 8 Back to Gallery

After three losses in the past four games, Stanford head coach David Shaw decided it was time for a change. He’ll start redshirt sophomore Keller Chryst at quarterback instead of Ryan Burns in Saturday night’s game at Arizona.

Shaw said Burns has played well at times, particularly against USC and during the game-winning drive against UCLA.

“He’s accomplished a lot in a little over half a season, but we need more production from the position,” Shaw said.

Stanford (4-3, 2-3 Pac-12) has just four touchdowns from its offense in the past five games and ranks last in the conference in scoring offense and total offense. The Cardinal have committed 12 turnovers in the past four games.

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“You won’t find a more improved player over the last calendar year,” Shaw said of Burns.

Still, the redshirt junior ranks 10th in the Pac-12 in passer efficiency. Burns has thrown for five touchdowns and seven interceptions in his seven starts.

He had a particularly difficult outing in Saturday’s 10-5 loss to Colorado. He completed 16 of 29 passes for 170 yards, throwing three interceptions. Two other passes were nearly picked off.

He also fumbled once and was part of a botched exchange on a snap that foiled Stanford’s deepest penetration. The Buffs recovered at their 6-yard line in the fourth quarter. Burns threw interceptions on the Cardinal’s next two series.

Burns’ inconsistency is but one of a number of problems that have beset the offense, including a line that hasn’t pass-blocked very well and hasn’t consistently opened holes for tailbacks Christian McCaffrey and Bryce Love.

The line might be even more shorthanded at Arizona because both tackle/guard David Bright and guard Johnny Caspers are questionable with injuries. Freshman guard Nate Herbig might get his first start. Meanwhile, fullback Daniel Marx will miss his fifth game in a row and might miss more, Shaw said.

There was also bad news on defense. Starting cornerback Alijah Holder is out for the season. Holder missed three games with a shoulder injury he suffered against UCLA. He returned for the Colorado game but reinjured his right shoulder early in the second half.

“It’s so unfortunate,” Shaw said. “He and Quenton Meeks were a great tandem.”

Chryst, who played at Palo Alto High, was the backup to Kevin Hogan last year. Chryst completed 5 of 9 passes with one touchdown in four games. This season, he has played in every game but USC. Playing mainly one or two series in his appearances, he has completed 7 of 18 passes with no TDs and one interception.

Shaw said he expects Chryst to play the whole game against the Wildcats (2-5, 0-4), who have lost four in a row. “We’ve got a lot of confidence in what we know that he can do,” Shaw said “We feel good about putting in a game plan around his abilities.”

Chryst, who was not made available to discuss his first collegiate start, is the son of former 49ers offensive coordinator Geep Chryst and the nephew of Wisconsin head coach Paul Chryst.

Trent Irwin, the team’s leading receiver, agreed with Shaw that the whole offense should share the blame for the lack of production, but he said, “Sometimes you need to change a little bit up. I think they’re both great quarterbacks. The first year for a quarterback is always tough.”

The last time Stanford changed quarterbacks midseason was in 2012, when Hogan replaced Josh Nunes. Hogan started the last five games, and Stanford won all of them, including the Rose Bowl over Wisconsin.

Tom FitzGerald is a San Francisco Chronicle staff writer. Email: tfitzgerald@sfchronicle.com Twitter: @tomgfitzgerald