The Grizzlies guard made 22 of 30 shots from the field, including all four of his 3-point attempts, in the victory at FedExForum in Memphis. He also logged seven rebounds.
"I'm just thankful for my teammates and coaches," Morant told reporters. "They believe in my and have all the confidence in the world that I can go and make the right play.
"They were looking for me. They told me to go ahead and go get it."
One of Morant's best plays of the night came with about 2:18 left in the second quarter. Grizzlies center Steven Adams pulled down a rebound to start the play and fired a pass to Morant on the left flank. Morant caught the feed and dribbled around Spurs defender Joshua Primo, cut toward the rim, picked up his dribble just outside the paint and took flight, despite being surrounded by defenders.
Morant pulled the ball back in his right hand and stuffed the ball through the rim while being defended by 7-foot-1 center Jakob Poeltl.
He followed that play up with a buzzer beater to give the Grizzlies a 68-58 lead at the break. The Grizzlies outscored the Spurs 28-27 in the third and 22-20 over the final 12 minutes to ice the victory. Morant totaled 23 points in the second half.
"I guess it was just one of those nights," Morant said. "I was making shots and very confident."
De'Anthony Melton and Tyus Jones scored 15 and 13 points, respectively, for the Grizzlies. Lonnie Walker IV paced the Spurs with 22 points and guard Dejounte Murray added 21 points and eight assists. Poeltl totaled 16 points, 10 rebounds and four assists.
"He has a chance to be pretty good," Spurs coach Gregg Popovich said of Morant. "He's a beautiful player. It's not just that he's athletic. ... He makes decisions. He knows what's going on on the court. He passes the basketball and inherently understands space, knows where he is on the court and knows where everyone else is.
"You combine the cerebral part of his game with the athleticism and you got a special kid."
Morant, 22, is averaging a career-high 27.6 points, 6.6 assists and 5.9 rebounds per game this season.
The Grizzlies (43-20) next face the Boston Celtics (36-27) at 7:30 p.m. EST Thursday at TD Garden in Boston. The Spurs (24-38) host the Sacramento Kings (23-40) at 8:30 p.m. Thursday at the AT&T Center in San Antonio.