DALLAS -- Dennis Smith Jr. had more responsibility placed on this shoulders in his third NBA game and he didn't sweat it.

Smith scored 19 points to lead the Dallas Mavericks to their first win by knocking off the previously undefeated Memphis Grizzlies 103-94 at American Airlines Center on Wednesday.

"Smith's pretty clearly a gamer. He is unafraid," Mavericks coach Rick Carlisle said "Tonight was the biggest amount of responsibility we have put on him to start with that group and really be the main ballhandler. That's a lot of responsibility.

"He did a great job and was one of the main reasons we got off to a good start. He's playing to exhaustion more frequently now. He's asking out. His conditioning to the NBA game is improving every day. He's doing extremely well. Everybody played well, and we need everybody to play well."

Smith fueled a game-deciding kick in the fourth quarter, as the Mavericks (1-4) avoided starting 0-5 for a second straight season. Smith, the No. 9 pick in this year's draft, accounted for 10 points during a 15-5 run that gave Dallas a 98-85 lead with 4 1/2 minutes left.

When the final buzzer sounded, Smith spiked the ball and let out a scream to punctuate the victory. He made 8 of 12 shots, including 3 of 6 from beyond the arc, and dished out five assists.

"I know personally I was crunk," Smith said, summing up his mood. "I was tired of losing."

The Grizzlies (3-1) were searching for only the second 4-0 start in franchise history. Memphis, which had wins over Golden State and Houston in its first three games, played from behind for the majority of the game.

Dallas raced out to a 19-point lead early in the second quarter. Memphis made sporadic pushes to get within striking distance but could never climb all the way back.

"It was always some kind of boneheaded play (that) would come back to bite us, miss free throws, or we give up a timely 3," Grizzlies coach David Fizdale said. "But for whatever reason we kept digging, kept digging, but we can't get ourselves into that early hole like we did, especially on the road."

The Southwest Division foes tee it up against Thursday night in Memphis.

Wesley Matthews added 16 points for Dallas, with 10 coming in the first quarter. Harrison Barnes scored 15 and Dirk Nowitzki added 13 points. The Mavs also had big contributions from guards J.J. Barea (14 points) and Yogi Ferrell (10 points) off the bench.

Dallas shot 48.6 percent from the floor and knocked down 11 of 26 3-pointers.

Marc Gasol led the Grizzlies with 26 points (on 9-of-15 shooting) and 11 rebounds but went an uncharacteristic 3 of 8 at the foul line. It was his third double-double and third consecutive 20-point outing.

Gasol said the Grizzlies got away from what made them successful through the first three games.

"We didn't get stops, he said. "It's that simple. You don't get stops and you trade baskets, you don't have a chance to win. You don't get enough stops, you won't be able to get over the hump."

Mike Conley scored 21, grabbed five rebounds and had three assists. Reserve guard Tyreke Evans was the only Memphis player scoring in double figures with 13 points.

. The Grizzlies shot 45.8 percent from the floor.

Memphis had entered the day as one of four unbeaten teams in the league.

NOTES: The Mavs donated all proceeds from single-game ticket sales Wednesday to Hurricane Maria relief efforts in Puerto Rico, which is also PG J.J. Barea's home country. ... Memphis SF Chandler Parsons (rest) was out. ... Dallas G Devin Harris returned after missing three games following the death of his older brother. He scored six points. ... The Mavericks had at least six players in double digits for the third time in their first five games of the season. ... The Grizzlies and Dallas meet for a third time Nov. 22 in Memphis.