With Jimmy Garoppolo ruled out due to a concussion and not making the trip to Los Angeles, the Raiders have decided to start rookie quarterback Aidan O'Connell against the Chargers on Sunday, league sources told ESPN.

The Raiders are opting to go with O'Connell, a fourth-round draft selection, over veteran Brian Hoyer, who last won a start in October 2016. The two quarterbacks both received reps during practice last week while Garoppolo was in the concussion protocol, but O'Connell got the majority -- if not all -- of the reps at practice by the end of the week, according to sources.

O'Connell will make his first NFL start and attempt the first passes of his pro career in an AFC West divisional showdown at SoFi Stadium against a Chargers defense that enters Sunday giving up an average of over 450 yards per game through the first three games of this season.

O'Connell was a preseason standout this summer, drawing comparisons from some NFL scouts and executives to Brock Purdy, another late-round pick who got the opportunity to start last season for the San Francisco 49ers.

In three preseason games in August, O'Connell completed 43-of-62 passes (69.4%) for 482 yards and three touchdowns without an interception. He left some Raiders fans wondering why he wasn't the backup quarterback to open the season, when Las Vegas listed Hoyer as the No. 2 quarterback.

O'Connell also shined during his college career at Purdue, where he passed for 9,219 yards and 65 touchdowns.

"I think the preseason was valuable for me at the time, just to get out there and play and get it under my belt," O'Connell told ESPN on Friday. "But I think at this point it's pretty far gone and it's different teams and different schemes and different game plans for us. So I'm happy it happened, but it's time to move on, I think, and see what happens."

The Raiders signed Garoppolo to a three-year, $72.75 million free agent contract this offseason to replace nine-year starter Derek Carr, even as Garoppolo needed surgery on his left foot after coming to terms with Las Vegas.

Garoppolo, who suffered the concussion in last Sunday night's loss to the Pittsburgh Steelers, has missed at least 16 regular-season and playoff games because of injury since 2020.