Jaxson Dart could miss the rest of the season after tests showed the New York Giants quarterback's knee injury is more severe than initially anticipated, sources told NFL Network's Ian Rapoport and Mike Garafolo. Dart suffered the injury during the opening possession of Monday's 28-6 loss to the Los Angeles Rams.

Coach John Harbaugh said after the game that the Giants likely avoided a "devastating outcome" with Dart's knee. But sources said the second-year star will miss an extended period and is facing the possibility of season-ending surgery. Harbaugh said Tuesday that evaluations were ongoing and declined to comment further on his timeline.

"It's an ongoing conversation about the health of a player, of a person," Harbaugh said. "We've got to prepare for the range of possibilities." He expressed confidence in backup quarterback Jameis Winston.

The Giants lost Dart on their seventh snap when he was hit by Rams linebacker Byron Young, sending him into linebacker Josaiah Stewart. Winston struggled in relief, completing 11 of 27 passes for 111 yards and an interception. Dart, 23, was outstanding in the season-opening win over the Dallas Cowboys, throwing for 230 yards and three touchdowns.