Source - Raiders' Jimmy Garoppolo (back) won't play vs. Bears - ESPN

Las Vegas Raiders quarterback Jimmy Garoppolo will not play in Sunday's game against the Chicago Bears due to his back injury, a source told ESPN's Adam Schefter on Thursday.

Garoppolo did not practice on Wednesday because of the injury, which he sustained in Las Vegas' Week 6 victory over the New England Patriots.

Sunday's game at Chicago will likely feature backup quarterbacks starting for both the Raiders (3-3) and Bears (1-5). Bears quarterback Justin Fields is doubtful to start because of a dislocated thumb, putting rookie Tyson Bagent in line to start. Brian Hoyer relieved Garoppolo last Sunday, however, rookie Aidan O'Connell started for the Raiders in their Week 4 loss at the Los Angeles Chargers when Garoppolo was sidelined with a concussion.

Garoppolo was injured during the Raiders' final first-half drive but stayed in the game. He was in obvious pain in the huddle as he grabbed at his lower right back. After he did not return to the field after halftime — he left in an ambulance still wearing his game pants — the Raiders listed him as out with a back injury.

He had led the Raiders to a 13-3 halftime lead, but Hoyer played the second half. Hoyer was 6 of 10 for 102 yards against the Patriots, including a 48-yard pass to rookie receiver Tre Tucker on third-and-4 that was the Raiders' longest play from scrimmage this season.

In five games, Garoppolo has passed for 1,079 yards while completing 68.0% of his passes with seven touchdowns and an NFL-high eight interceptions for a passer rating of 82.6 and a Total QBR of 48.3.

ESPN's Paul Gutierrez contributed to this report.