The Detroit Lions had everything rolling on Sunday in a blowout 47-9 victory at the Dallas Cowboys, but then suffered what looks like a major loss.

Defensive end Aidan Hutchinson, Detroit’s best defensive player and an NFL Defensive Player of the Year candidate, was injured on a sack of Cowboys quarterback Dak Prescott in the second half. He winced in pain as he wrapped up Prescott, then stayed down. A cart came on the field for him.

The replay showed that as Hutchinson spun around while wrapping up Prescott, his leg hit a teammate. The force of the blow caused what looked like a broken leg for Hutchinson. Players from both sides came on the field as Hutchinson was being loaded on the cart, and an air cast was put on his injured left leg.

WARNING: The replay on Fox is graphic.

Lions head coach Dan Campbell confirmed after the game that Hutchinson will undergo surgery for a fracture in his leg, and that he’ll stay in Dallas to get that done. A specific timeline for his recovery isn’t known. The Lions confirmed after the game that Hutchinson sustained a tibia injury, but that it was not a compound fracture as initially thought.

“He’s in good hands right now,” Campbell said. “He’s being taken care of … Obviously he’s going to be down for a little while. So that’s tough, man. It’s hard when you lose somebody like him.”

Early Monday, the Lions announced Hutchinson underwent successful surgery to repair a fractured tibia and fibula. He’ll be returning to Detroit this week and is expected to make a full recovery, but there is currently no timeline for his return to play.

The Lions led the Cowboys 34-6 at the time of Hutchinson’s injury. They were on their way to improving to 4-1 and have looked like one of the best teams in the NFL. But losing Hutchinson for a while would severely impact their hopes of making the first Super Bowl in franchise history.