The 49ers fear star defensive end Nick Bosa suffered a season-ending knee injury Sunday, ruining what little joy they took from a victory riddled with fallen players on the MetLife Stadium turf.

Bosa has anterior cruciate ligament damage to his left knee, Kyle Shanahan told reporters following the 31-13 win over the Jets. The coach didn’t elaborate, but the strong belief is Bosa tore his ACL, which would leave San Francisco without one of the league’s best defensive players for the remainder of the year.