PHOENIX -- Isaiah Thomas scored a game-high 28 points in his return to Phoenix and the Boston Celtics, after squandering a 21-point lead, held on to beat the Suns 102-99 Saturday night.

Devin Booker capped an 8-2 run with a step-back jump shot that pulled Phoenix within 98-97 with 1:16 remaining. Booker had a chance to give the Suns the lead on their next possession, but his 20-footer bounced off the back of the rim.

Phoenix got another opportunity when Thomas missed a 3-point attempt from the right elbow but Brandon Knight threw up a 25-foot 3-pointer that fell well short of the rim.

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Thomas handed the Suns a final chance when he missed one of two free throws with 13.9 left, but Turner blocked Booker's driving attempt with 3.9 seconds to go to secure the win.

Thomas, sent to Boston by the Suns just ahead of the trade deadline in 2015, was only 8-for-20 from the floor in his first game back in the arena where he played for four often tumultuous months, but was 9-of-10 from the floor.

Turner scored 17, Kelly Olynyk added 16 and Avery Bradley added for the Celtics (43-30), who won their fourth straight and moved a half-game ahead of Miami for fourth place in the Eastern Conference.

Booker, after scoring just two points in the first half, finished with 21 and Knight added 19 for the Suns (20-53), who have lost two straight and three of four.

The Celtics led by as many as 21 in the first half and held a 64-44 lead with 10:12 left in the third quarter, only to watch the Suns come roaring back.

PJ Tucker and Knight each converted 3-point plays and Knight scored nine points total as Phoenix outscored Boston 29-10 over the next seven-plus minutes. Booker's dunk off a pass from Tucker pulled the Suns within 74-73 with 2:43 to go in the quarter.

Thomas steadied the Celtics, scoring seven straight points to close the quarter and help Boston take an 81-75 lead after three.

Boston pushed the lead back to 10, 86-76, on an Olynyk lay-in off an offensive rebound with 10:56 remaining before the Suns mounted their late fourth-quarter comeback.

NOTES: Boston G Avery Bradley flew to Phoenix from Boston earlier Saturday after being hospitalized with an undisclosed illness. ... Celtics F Jae Crowder, who has missed the last six games with a high ankle sprain, did not play Saturday and also will miss Monday's game against the Los Angeles Clippers. ... Suns F Jon Leuer was scratched with an upset stomach. G/F John Jenkins, a starter Friday night at guard, took Leuer's starting spot as the small forward. ... Suns G Ronnie Price and G Brandon Knight, also battling stomach ailments, dressed. ... Suns C Tyson Chandler missed his third straight game with back spasms. ... The Suns were playing the back half of their last set of back-to-back games. ... The 1975-76 "Sunderella Suns" were honored at halftime of the game. That Suns squad reached the NBA Finals before losing in six games to the Celtics, one of two Phoenix teams to make the championship series in the franchise's 47 seasons.