Shai GIlgeous-Alexander scored 22 of his 34 points in the second half to rally the Oklahoma City Thunder from a 14-point deficit and earn a crucial 100-96 victory over the Dallas Mavericks in Monday's Game 4 of a Western Conference semifinal series.

Chet Holmgren had 11 of his 18 points after half-time and added nine rebounds to help the top-seeded Thunder even the best-of-seven series at 2-2 as it heads back to Oklahoma City for Wednesday's all-important Game 5.

The fifth-seeded Mavericks squandered an opportunity to put the Thunder on the brink of elimination despite setting a franchise play-off record with 13 blocks, including four each from Derrick Jones Jr. and rookie Dereck Lively II.

Jones finished with 17 points in the loss, while Luka Dončić registered a triple-double for Dallas with 18 points, 12 rebounds and 10 assists. 

The Mavericks led the majority of the game and owned an 86-80 advantage just past the midway point of the fourth quarter before Oklahoma City began its late surge. The Thunder seized momentum with a 12-2 run, capped by consecutive 3-pointers from Holmgren and Luguentz Dort, to go up 92-88 with 2:14 remaining.

Dallas answered on Tim Hardaway Jr.'s 3-pointer on the ensuing possession, but back-to-back baskets by the Thunder's Jalen Williams gave Oklahoma City a 96-91 lead entering the final minute.

The Mavericks again responded and had a chance to tie it when Doncic was fouled with 10.1 seconds left with Dallas trailing 96-94. The MVP finalist made just one of his two shots, however, and the Thunder sealed the outcome by going 4 for 4 from the foul line in the waning moments.

Free throw shooting played a part in the result, as Oklahoma City finished 23 of 24 from the line compared to 12 of 23 for Dallas.

The Mavericks held a 54-43 lead at half-time after limiting the Thunder to under 35 per cent shooting for the first two quarters, and stretched the margin to 14 when P.J. Washington hit a 3-pointer to begin the third.

Oklahoma City closed the gap before the end of the period, though, as it ended the third quarter on a 9-2 run to pull within 69-65 entering the fourth.

Celtics handle injury-plagued Cavaliers to take 3-1 lead

In the East, the top-seeded Boston Celtics moved within a game of reaching the conference finals for a third straight year after posting a 109-102 Game 4 win over the shorthanded Cleveland Cavaliers behind Jayson Tatum's 33 points and 11 rebounds. 

Jaylen Brown added 27 points to help Boston take a 3-1 series lead over a fourth-seeded Cavaliers team playing without leading scorer Donovan Mitchell. The All-Star guard was unavailable due to a strained left calf he sustained in Cleveland's 106-93 loss in Saturday's Game 3.

The Cavaliers also remained without starting center Jarrett Allen, who hasn't played since Game 4 of their opening-round series against Orlando due to a rib contusion.

Darius Garland kept Cleveland competitive by producing 30 points and seven assists, while Caris LeVert had 19 points starting in place of Mitchell.

Boston can close out the series at home in Wednesday's Game 5.

Tatum set the tone right from the outset, scoring 16 points on 6-of-9 shooting in the first quarter to stake the Celtics to a 37-30 lead after one period.

The All-Star forward closed out the first half with a 3-pointer that sent Boston into the break with a 62-57 advantage, though Cleveland opened the third quarter on an 8-2 run to move ahead by a 65–64 score three minutes into the second half.

Boston re-asserted control from there, however, as it outscored the Cavs by a 14-4 margin over the next 4 1/2 minutes. Brown had seven points during the spurt, which Derrick White capped with a 3-pointer for a 78-69 Celtics' lead with 4:50 left in the third quarter.

The Celtics stretched the lead to 98-83 with under eight minutes left, though Cleveland kept battling and put together a 12-2 run to close the gap to 100-95 with three minutes left to play.

Brown hit a clutch 3-pointer with 1:09 to go, however, to put Boston up 105-97, and the Celtics kept Cleveland at bay the rest of the way as White and Tatum each made two free throws in the closing stages.