New York Giants quarterback Jaxson Dart could be sidelined for an extended period after additional testing revealed that the knee injury he suffered Monday night may be more serious than initially believed, according to ESPN.

The 23-year-old quarterback is reportedly dealing with a significant injury that could potentially require surgery and bring his season to an early end. The Giants have not yet officially confirmed the full extent of the damage.

Dart went down just minutes into New York’s 28-6 loss to the Los Angeles Rams. On a third-down play, he was pressured by Rams linebacker Byron Young, who made contact with Dart from the right side. Dart was then hit low by linebacker Josaiah Stewart, causing his legs to buckle as he went down hard.

After briefly remaining on the field, Dart was able to make his way to the sideline under his own power, although he was noticeably limping. He was examined in the medical tent before heading to the locker room.

Jameis Winston took over at quarterback on the Giants’ next possession and played the remainder of the game. Dart returned to the sideline during the second half but was dressed in street clothes.

Dart completed 3 of 5 passes for 20 yards before leaving the game.

Following the injury, Giants head coach John Harbaugh declined to confirm reports that Dart had suffered an MCL sprain, saying the team would have a clearer picture after Tuesday’s MRI.

“That’s in the neighborhood of it, I would say,” Harbaugh said.

The Giants are now awaiting the results of the additional medical evaluation to determine the severity of the injury and how long Dart could be unavailable.