DALLAS -- Kawhi Leonard made his long-anticipated season debut Tuesday night and looked to be in midseason form, although his San Antonio Spurs fell apart in the fourth quarter without him and lost to the Dallas Mavericks 95-89 at American Airlines Center.

The Spurs' All-Star forward missed the first 27 games of the season because of a quad injury. Upon returning to the starting lineup, he quickly displayed his all-around excellence, producing 13 points on 6-of-12 shooting and adding six rebounds, one assist, one steal and a block.

He did it all in only 16 minutes as coach Gregg Popovich promised a gradual reintroduction. Leonard's lone offensive rebound was a tip-out to himself that led to a bucket for a 55-50 Spurs lead midway through the third quarter, and Popovich pulled him soon after.

Leonard made his way to the locker room toward the end of the third quarter, raising a few eyebrows, but his early exit from the floor apparently was for planned treatment. Afterward Popovich said Leonard's performance was "wonderful," but that it was frustrating for him to sit out the fourth quarter because he felt he had just started to get loose.

The Spurs' slippage without Leonard the rest of the way raised Popovich's ire. Dallas, sparked by guard J.J. Barea's aggressive drives to the basket, opened the fourth quarter on an 8-0 run, went up 91-80 with 4:01 to go and held on to snap the Spurs' four-game winning streak as well as end their own three-game skid.

"He's trying to get some rust off and that kind of thing. Obviously he's confident. He's a heck of a player," Popovich said of Leonard. "And it was really frustrating for him to just start getting loose and have to come off the court, so that's a tough situation for him."

Dallas (8-20) got the win without speedy rookie point guard Dennis Smith Jr. (hip). However, the Mavericks appeared headed for another tough loss after forcing the Spurs to play from behind in the first half.

The Mavs' 11-point, second-quarter lead slipped to 46-44 at halftime, and a 7-0 run by the Spurs to start the third quarter gave San Antonio its first lead since 2-0.

However, without Leonard, the Spurs' offense missed eight consecutive shots during a 13-1 Dallas run early in the fourth.

Harrison Barnes led the Mavs with 17 points while Barea, Wesley Matthews and Yogi Ferrell each scored 16. Reserve forward Dwight Powell notched his first double-double of the season with 12 points and 12 rebounds.

"We have been waiting for a game like this where we go out and play a full 48-minute game," Ferrell said. "We've had some good games this season, but we put it all together tonight even when they made a run in the third quarter."

LaMarcus Aldridge led San Antonio with 23 points and 13 rebounds. While he paced the team, Dallas managed to hold him to 9 of 23 from the floor after he scored 65 points in the Spurs' two victories against the Mavs this season.

"We were in much more of a scrambling mode and frenetic, I would even say. That is what it is going to take for us," Mavs coach Rick Carlisle said of his team's defensive effort. "I was really happy for our players. They have been fighting so hard and not getting much in terms of rewards for it. But, tonight, it was a win that was really earned."

Rudy Gay was the only Spurs player other than Aldridge and Leonard to score in double figures, finishing with 21 off the bench.

Leonard, Popovich said, will continue to be on a minutes restriction when the Spurs return to action Friday against the Houston Rockets.

"He looked good," Aldridge said. "It's going to take time to get back to the Kawhi that we know. I thought he looked good. First game in a long time. He looked comfortable out there making plays."

NOTES: The Spurs lost in Dallas for the first time in six games. ... San Antonio coach Gregg Popovich needs seven more victories to pass George Karl (1,175) for fifth on the NBA's all-time list. ... Mavs G Dennis Smith Jr. missed his third consecutive game because of a hip injury, and coach Rick Carlisle said he also would miss the next two games at Golden State and San Antonio. ... F Dirk Nowitzki moved five rebounds away from passing Bill Bridges (11,054) for 28th on the league's all-time list.