Shai Gilgeous-Alexander scored 39 points to lead the Oklahoma City Thunder to a 118-104 win over the visiting Dallas Mavericks on Tuesday night in the Western Conference quarterfinals of the NBA Cup.

Oklahoma City will play the Warriors or Rockets in Las Vegas on Saturday, with the winner advancing to the championship game of the in-season tournament. Golden State and Houston will collide in the semifinals on Wednesday.

The Thunder’s win, their fourth consecutive, snapped Dallas’ seven-game winning streak.

Gilgeous-Alexander did a lot of his damage from outside, hitting five of Oklahoma City’s season-high 20 3-pointers (on 50 attempts). The star guard also had eight rebounds and five assists.

Defense also paved the way for the Thunder, who scored 36 points off of 19 Mavericks turnovers. Oklahoma City also held Dallas stars Luka Doncic (16 points on 5-of-15 shooting) and Kyrie Irving (17 points on 7-of-14 shooting) in check.

Doncic added 11 boards while Klay Thompson and Naji Marshall each posted 19 points for the Mavericks.

Oklahoma City took charge in the third quarter, turning a three-point halftime lead into a 90-73 advantage heading into the final 12 minutes of action. Gilgeous-Alexander went off for 16 points in the third, nine of which came during a 13-2 run to open the period.

It was a 20-point game early in the fourth, as the Thunder were up 97-77 following a hook shot from Jalen Williams with 10:34 to go.

Back-to-back triples from Irving punctuated a 10-0 run from Dallas that made it 97-87, and the Mavericks later had their deficit down to eight, 100-92, thanks to an Olivier-Maxence Prosper 3-pointer with 7:50 remaining.

However, Oklahoma City scored the next 11 points to put the game away.

Williams chipped in 18 points for the Thunder, who also got 11 apiece from Luguentz Dort and Cason Wallace.

Oklahoma City held a 57-54 lead at the break. Doncic couldn’t get anything going in the first two quarters, scoring two points on 1-of-7 shooting.