Shai Gilgeous-Alexander delivered a stellar performance, scoring 39 points to lead the Oklahoma City Thunder to a 118-104 victory over the Dallas Mavericks on Tuesday night in the NBA Cup quarterfinals. The Thunder improved to 19-5 this season, advancing to the semifinals in Las Vegas.

Jalen Williams contributed 18 points, while Isaiah Hartenstein tallied 10 points and 13 rebounds for Oklahoma City. The Thunder will face the winner of Wednesday’s Golden State-Houston matchup on Saturday.

The game served as a rematch of last season’s Western Conference semifinals, which the Mavericks won 4-2. This time, the Thunder held Dallas in check, thanks to their defensive prowess.

Luka Doncic, the Mavericks’ centerpiece, was limited to 16 points on 5-for-15 shooting, with Lu Dort, Alex Caruso, and rookie Cason Wallace anchoring the defensive effort.

Gilgeous-Alexander set the tone early, scoring 18 first-half points as Oklahoma City took a 57-54 halftime lead. Dallas struggled to find its rhythm, with Dončić managing just two points before the break.

In the third quarter, Gilgeous-Alexander dominated, scoring 16 points on 7-for-8 shooting during a decisive 13-2 run that helped the Thunder extend their lead to 90-73. Isaiah Joe capped the quarter with a deep three-pointer at the buzzer.

The Mavericks (16-9) failed to recover, committing 19 turnovers that resulted in 36 Thunder points. Dallas shot 50% in the first half but cooled off significantly, hitting just 6 of 19 field goals in the third quarter.

Naji Marshall and Klay Thompson paced the Mavericks with 19 points each, while Kyrie Irving added 17 points. P.J. Washington, a key contributor in Dallas’ past wins over Oklahoma City, was sidelined with an illness.

Hartenstein, signed in the offseason to bolster Oklahoma City’s interior presence, proved pivotal as the Thunder outrebounded Dallas 52-44. His presence allowed Oklahoma City to maintain control on the boards and limit second-chance opportunities.

The Thunder’s depth also played a role, with solid contributions from Isaiah Joe, Alex Caruso, and Kenrich Williams, who combined for 24 points off the bench. Caruso’s defense and three-point shooting helped Oklahoma City keep the Mavericks at bay in the fourth quarter.

Dallas struggled with consistency from its supporting cast. The absence of Washington compounded issues for a Mavericks team that relied heavily on Doncic and Irving to generate offense.