BOSTON — The Phoenix Suns rely on their fast-break offense. It was Eric Bledsoe’s defense that keyed their latest win.

Markieff Morris scored a career-high 30 points and Bledsoe had a key steal and breakaway dunk in the closing minute to lift the Suns to a 118-114 victory over the Boston Celtics on Monday night.

With the score tied at 114, Bledsoe stole Avery Bradley’s cross-court pass and went in alone for a dunk, pushing the Suns ahead with 29.5 seconds to play.

“He’s not afraid to make that calculated gamble at the end of games,” Phoenix Coach Jeff Hornacek said. “We sometimes live with some of his decisions on going for steals because he did it a bunch last year, too. He gets big steals at the end of games.”

Goran Dragic had 22 points, Alex Len scored 19 with seven rebounds and Bledsoe finished with 15 points and seven assists for the Suns, who lost their previous two games.

“It was big because we had two losses back-to-back,” Len said.

Jeff Green led Boston with 28 points, and Jared Sullinger had 18 points with eight rebounds. Rajon Rondo fell one assist shy of a triple-double with 14 points, 10 rebounds and nine assists.

Tyler Zeller added 19 points and seven rebounds for the Celtics, who lost their third straight despite rallying from a double-digit deficit.

“We’re not there yet and that’s frustrating,” Boston Coach Brad Stevens said of his team’s 3-6 start.

Sullinger knows that falling into a deep hole makes it hard to bounce back and beat good teams.

“It takes every ounce of energy to make a comeback,” he said. “We just have to play better.”

After Bledsoe’s dunk, Green’s long 3-point attempt rimmed out and Len grabbed the rebound. He was fouled and hit both from the line to put the Suns up 118-114 with 19.8 seconds left.

The lead had changed six times in a wild, up-and-down fourth quarter until Green’s fast-break dunk put Boston ahead with just under a minute to go. He was fouled on the play and hit the free throw, making it 114-112 with 57.3 seconds to go.

Dragic then got free for a backdoor layup, tying it at 114 with 46 seconds remaining.

Boston took a 105-104 lead on Green’s driving basket down the lane.

Phoenix opened the third quarter by scoring 11 of the first 13 points, opening its biggest lead of the game on Marcus Morris’ 3-pointer from the right corner. But, just as they did in the first half, the Celtics came charging back, closing to 89-88 on Zeller’s dunk at the end of the quarter.