Speculation swirls on severity of Giants QB Jaxson Dart's injury. Here's what John Harbaugh had to say.

The Giants' season of promise may be on the verge of falling apart.

According to a report from ESPN NFL insider Adam Schefter, quarterback Jaxson Dart's knee injury, originally thought to be a left MCL sprain, is worse than initially thought and the second-year quarterback could be looking at season-ending surgery.

Dart, who had an MRI on Tuesday, was injured early in Monday night's 28-6 loss to the Los Angeles Rams when he was sandwiched by two defenders while dropping back to pass. He was down on the field for a few minutes before walking off the field under his own power and later limping to the locker room. He was originally listed as questionable to return, but was later ruled out.  

During a news conference on Tuesday, Giants head coach John Harbaugh did not confirm a season-ending injury.

"Right now, the evaluations are ongoing. We haven't got any final decisions yet. We've learned a lot more," Harbaugh said. "I wouldn't really want to share too much until decisions get made, and that takes more than one person. It takes everyone involved, so when we know what direction we're going to have to go, or whatever it might be, we'll announce that. But we don't have that yet, so I don't want to get out over our skis on that."

Before leaving the game, Dart completed 3 of 5 passes for 20 yards. He was relieved by veteran Jameis Winston, who finished 11-of-27 for 111 yards and an interception.

Dart got his sophomore season off to a great start by going 23-of-29 for 230 yards and three passing touchdowns in the Giants' 28-20 win over the Dallas Cowboys in Week 1. Winston, a veteran of four teams with plenty of experience as a starter during his 12-year-career, signed a two-year, $13 million contract extension on Sept. 7.

The Giants (1-1) host the Tennessee Titans on Sunday at 1 p.m.  

This is a developing story. Please check back with CBS News New York for updates ...