Shai Gilgeous-Alexander scored 31 points, Jalen Williams added 26 and Chet Holmgren scored 23 of his 24 points in the second half to spark the second-largest NBA playoff victory fightback since 1997.
"It wasn't pretty. They hit us first. But we did what we had to do and came away with a win," Holmgren said. "It was a team mentality. Everybody was saying something when we went into that locker room. Then we came out and we cleaned it up."
Oklahoma City seized a 3-0 lead in the Western Conference first round best-of-seven series with a chance to complete the sweep in game four at Memphis on Saturday.
Morant suffered a bruised left hip late in the second quarter when he drove to the hoop and leapt high into the Thunder's Luguentz Dort and fell face-first onto the court, writhing in pain for several minutes and eventually leaving the game for good.
The Grizzlies took their largest lead at 69-40 seconds after Morant's departure with 3:15 to play in the second quarter and Memphis led 77-51 at half-time, but Oklahoma City outscored the hosts 63-31 in the second half.
Memphis interim coach Tuomas Iisalo said the injury to Morant, the Grizzlies' points and assist leader this season, sapped his team's energy and ability to execute plays.
"I would say quite drastically from the result, not only the energy but the execution," Iisalo said.
"We did a great job fighting for 48 minutes but against this team, it's not enough to fight. You also have to be able to execute."
As for Morant, he added: "He's going through further evaluations tomorrow and then we'll know more."
Great response
The only greater NBA playoff collapse in the past 25 years came in 2019 when the Los Angeles Clippers rallied from 31 points down to defeat Golden State.
"Our response, in a game that doesn't feel attainable in certain parts of it, was great," Thunder coach Mark Daigneault said.
The Morant injury play evoked memories of Golden State's Jimmy Butler falling awkwardly Wednesday, with an MRI on Thursday reportedly showing a deeply bruised gluteus muscle that left him uncertain for game three against Houston on Saturday.