Thaddeus Young, Myles Turner and Darren Collison explain how Victor Oladipo's attitude will help the Pacers as he recovers from a leg injury. (1:28)

A preliminary exam has left the Indiana Pacers fearful that All-Star guard Victor Oladipo suffered a season-ending right knee injury Wednesday night that will require surgery, league sources told ESPN.

Oladipo will undergo an MRI on Thursday in Indianapolis for a full accounting of the damage, the team said.

"It is a serious injury and we'll know more after the MRI," coach Nate McMillan said. "We're not going to speculate. It's a tough situation. That kid has a beautiful spirit about him. He has always been one to try and to lift us up. We've got to lift him now."

Pacers officials were preparing for the worst: the loss of the franchise's most important player as the team competes with the elite of the Eastern Conference.

Oladipo crumpled to the floor during Wednesday night's home game against the Raptors after falling in an attempt to disrupt a pass to Toronto's Pascal Siakam. Oladipo's leg bent awkwardly on his way to the court.

"I didn't see what happened," Siakam said. "Watching the replay, he stuck his leg while he was falling. That's when he hit me. It's just an unfortunate situation. It's really scary. It's tough."

The severity was evident almost immediately as trainers draped a towel over Oladipo's leg and players from both teams surrounded him while he was down. He received a standing ovation from fans as he was carted off the floor on a stretcher and responded by waving to the crowd.

Oladipo has transformed the Pacers since his arrival in 2017 from the Oklahoma City Thunder, developing into an All-Star for the first time in the 2017-18 season. He is the Pacers' leading scorer this season, with 18.8 points per game.

Despite losing Oladipo in the second quarter, the Pacers defeated the Raptors 110-106 to move to 32-15 on the season. They are third in the Eastern Conference.

"We've got to come together and play inspired basketball," Myles Turner said. "We can't let this get us stuck in the mud. It's emotional, but we have to overcome it and play."

Information from The Associated Press was used in this report.