Joel Embiid was right to be concerned in the hours after a head-on collision.

The 76ers center was diagnosed with a concussion and an orbital fracture of his left eye after undergoing evaluations at a Pennsylvania hospital, the team announced Thursday evening. The fracture requires surgery, which will be performed in the coming days.

Though the team gave no timetable for his return, Embiid is expected to be back in two-to-four weeks, according to ESPN.

Embiid looked woozy after hitting heads with Markelle Fultz on a botched hand-off during the second quarter of Philadelphia’s 118-101 win over the Knicks Wednesday night. He immediately put his head in his hands and collapsed to the floor, lying there until trainers helped him to the locker room.

The 24-year-old initially passed concussion tests, but after he continued to experience symptoms, he was ultimately diagnosed and placed in the league’s concussion protocol.

Embiid, a first-time NBA All-Star this season, has been a key part of the 76ers’ success as they prepare for their first playoff berth since the 2011-12 season.