The Las Vegas Raiders didn't just lose a key rivalry game -- and serious ground in the AFC playoff race -- on Thursday night. They also lost their starting quarterback, with Marcus Mariota replacing an injured Derek Carr after the team's second possession. And it doesn't appear they'll be getting him back anytime soon. Asked to update Carr's health after Thursday's loss to the Chargers, coach Jon Gruden said the QB's groin injury is "pretty significant," suggesting Mariota could be in line to start in Week 16.

"I don't believe it's a real tear," Gruden told reporters, "but obviously if he can't finish the game, it's got to be pretty significant ... So it was tough."

Carr, who hasn't missed a game in three seasons, was initially ruled questionable to return after a first-quarter red-zone run left him hobbled. By the second half, he'd been ruled out entirely, with Mariota going on to account for over 300 total yards and two touchdowns in the Raiders' 30-27 defeat.

It's unclear if Carr will practice this week, but Gruden's early remarks indicate it's very possible Mariota will be forced to take over as the Raiders' signal-caller for at least Week 16 against the Miami Dolphins (8-5). The former Tennessee Titans veteran has 61 career starts under his belt and was signed in March to a two-year, $17.6 million deal as one of the NFL's highest-paid backups.