Zach Randolph had 25 points and 13 rebounds, and the Memphis Grizzlies overcame a 21-point deficit in the second half to defeat the Boston Celtics 101-98 on Sunday.

Isaiah Thomas, who led the Celtics with 35 points, launched a 3-pointer as time expired but officials confirmed the basket came after the horn, giving Memphis its biggest comeback victory of the season.

Mario Chalmers added 18 points for the Grizzlies, hitting 11 of 13 free throws. Tony Allen finished with 15 points and 10 rebounds. Matt Barnes added 12 points and Marc Gasol scored 11 on 5-for-17 shooting.

Amir Johnson and Avery Bradley had 14 points apiece for Boston. Johnson also grabbed nine rebounds. Jared Sullinger scored 11 points, Jae Crowder added 10 and Thomas had eight assists.

Memphis trailed by 21 early in the third quarter, but scored 14 straight points to put a dent in the Celtics’ advantage. Boston regained a double-digit lead in the fourth, but Memphis chipped away and eventually led by five several times late in the game, the final time with 9.7 seconds remaining.

The Grizzlies converted all 12 of their free throws in the final 3:08 after the game was tied at 87. Those free throws allowed Memphis to maintain a three- to five-point lead in the final 34 seconds.

The Celtics dominated the first half, building the lead to as many as 18 with good ball movement that provided Boston easy inside baskets at times. Thomas already had 15 points at the break, and Crowder had 10 as Boston held a 53-38 lead at halftime.

Memphis allowed the Celtics to shoot 57 percent in the first quarter. Randolph had 12 points off the bench early, but that was the extent of a sustained offense. The Grizzlies shot 30 percent from the field in the half.

Boston started the second half by pushing the lead to 21, but Randolph continued to score inside and got help from Chalmers, who had 12 points in the third quarter.

The rally got Memphis to 63-58, but Boston maintained a 76-68 lead after three.

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