Johan Petro got his first start of the season Friday.

The Hawks, missing Zaza Pachulia and Ivan Johnson, turned to the 7-footer against the Celtics at TD Garden.

Pachulia (right Achilles) missed this third consecutive game with a recurrence of the ailment. Ivan Johnson (personal reasons) was also not available. Neither player traveled with the team to Boston. Their status for Saturday’s game against the Nets is uncertain.

Despite the missing big men, the Hawks started Petro in an attempt to match size with the Celtics. Petro was effective against the Lakers on Sunday when he had six points, eight rebounds, four steals, two blocks and one assist in 24 minutes.

“He played well,” Hawks coach Larry Drew said. “But we are in a situation where we are short big men, and he’ll have to play minutes.”

Petro said after the Lakers game, in facing Dwight Howard, he tried to be active and use his length.

Still winning: The Celtics are 13-4 since losing All-Star point guard Rajon Rondo in a game against the Hawks in January. Drew said the Celtics are now unpredictable on offense.

“Even losing Rondo, watching their team play, they haven’t really missed a bit,” Drew said. “In fact, they look stronger to me from the fact that they lose a little predictability. With Rondo on the floor, you know the ball is going to be in his hands the majority of the time. Now, with him out the ball is in a lot of different hands, and they are doing a really good job moving the ball.

“To me, they become even tougher to defend. On any given night three or four guys on that team can have four or more assists easily.”

Etc.: DeShawn Stevenson was not scheduled to play against the Celtics in the opening game of back-to-backs. The plan is for the swingman to play against the Nets and guard Joe Johnson. … The Hawks at Heat game Tuesday will be televised by NBA TV after a fan vote.