BOSTON — Rajon Rondo returned from a broken hand and had 13 points, 12 assists and seven rebounds in the season opener Wednesday night to help the Boston Celtics beat the Brooklyn Nets 121-105.

Kelly Olynyk had 19 points and Jeff Green added 17 for Boston, which opened a 29-point lead at the end of the third quarter and coasted to the win.

Mirza Teletovic had 20 points and six rebounds in 23 minutes off the bench for the Nets. Joe Johnson scored 19 points for Brooklyn, and Deron Williams had 19 points and eight assists.

The Nets trailed for all but a pair of free throws that opened the game.

Rondo said he didn’t decide to play until about an hour before the tipoff, after waking up from a pregame nap and feeling ready to play. With the point guard missing all the exhibition season, coach Brad Stevens wasn’t sure what he could expect.

But Rondo, wearing a black brace on his left wrist and hand, showed no ill effects of the injury, dribbling with both hands and shooting 6 for 9 — better than his career 47.5 shooting percentage. He was 0 for 4 from the free throw line.

The Celtics led 101-72 at the end of the third quarter, but Brooklyn went on a 12-2 run to start the fourth and cut the deficit to 19. The Nets made it 112-97 on Johnson’s 3-pointer with 4 minutes left but couldn’t come any closer until the final seconds.

Rondo’s return on opening night stole some of the attention from ex-Celtic Kevin Garnett, who received a big cheer when he was introduced with the starting lineups and went on to score 10 points with six rebounds.

The 38-year-old Garnett played six seasons in Boston, leading the Celtics to the NBA finals twice and the team’s unprecedented 17th championship in 2008. He picked up a technical foul late in the game, prompting a “KG!” chant from the crowd. The Celtics opened a 21-12 lead in the first period and led by 10 with four minutes left in the second when they went on a 17-1 run to close the half. Marcus Thornton had eight points in the second quarter, and Rondo had four more assists to give him nine for the half.