Stanford quarterback Keller Chryst will have knee surgery and miss at least six months as the result of an injury suffered in the Sun Bowl, according to multiple sources.

Chryst has severe ligament damage; the specifics of the injury, however, have not been disclosed by the school.

The recovery timeline means Chryst, in a best-case scenario, could be on the field in a limited capacity when the Cardinal starts training camp in late July or early August.

His absence takes on greater significance because of another development: Senior Ryan Burns, who replaced Chryst in the Sun Bowl (and started the first seven games of the season) is expected to leave Stanford under the NCAA’s graduate transfer policy.

With Burns gone and Chryst recovering, the Cardinal has one scholarship quarterback for offseason workouts and spring practice: freshman K.J. Costello.

Cardinal coach David Shaw was not available to comment on the state of the quarterback position. His next scheduled media session is Feb. 1, National Signing Day.

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Chryst, the former Palo Alto High School star, injured his right knee on a running play late in the first quarter against North Carolina.

Everything about the incident — from his immediate reaction and the in-game treatment by the medical staff to the prognosis and the delay in having surgery (to let swelling subside) – suggests a torn anterior cruciate ligament.

The exact nature of the injury will frame the timeline for recovery. Sources said Chryst, a junior, will miss at least six months from the time of surgery, which would peg his return to late July or the first half of August, at the earliest.

A longer rehabilitation would likely rule out Chryst’s availability for the start of the season, which itself is a moving target.

Stanford is expected to face Rice in Sydney, Australia, one week earlier than the official opening for most major college teams.

If the Sydney event is finalized for Aug. 26, the Cardinal would have a week off to recover and play its second game, expected to be the Pac-12 opener, on Sept. 9.

That, sources said, could be the preliminary target date for Chryst’s return to the lineup.

But for the next six months, at least, Costello will run the offense.

A highly touted prospect from Santa Margarita Catholic, the alma mater of Warriors guard Klay Thompson, Costello served as Stanford’s scout team quarterback during the 2016 season. At 6-foot-5 and possessing a strong arm, he was considered worthy offseason competition for a healthy Chryst.

The other quarterbacks on the roster, Brent Peus and Jack Richardson, are preferred walk-ons. Both will receive more practice repetitions than they could have imagined a few weeks ago.

Burns’ destination for his final year of eligibility is not known.