Celts without Ray Allen for Game 1

ATLANTA -- Boston Celtics guard Ray Allen was out for Sunday's Game 1 of an Eastern Conference quarterfinals series against the Atlanta Hawks. Without Allen, the Celtics lost 83-74.

Allen went through a pregame warm-up on the court at Philips Arena, but simply was not ready to dive back into action due to a balky right ankle. Earlier in the day at the team's shootaround, he expressed hesitation in getting back on the court if his lingering ankle soreness made him a liability, particularly given the increased intensity of playoff basketball. Despite his absence, Rivers remains confident he will play moving forward.

"It's going to be day to day, game to game," said Rivers before the game. "That's just what it is."

Meanwhile, the Hawks were without center Zaza Pachulia.

Coach Larry Drew announced before Sunday's contest that third-stringer Jason Collins would start at center, sticking with the lineup that went 5-1 after Pachulia sprained his left foot on April 13. Collins had six points and five rebounds in the win.

Drew says Pachulia's foot is getting better and it will be a game-to-game decision on whether he plays in the series. The Hawks already have played most of the season without top center Al Horford, who is recovering from pectoral surgery.

Marvin Williams will continue to come off the bench for the Hawks. The 7-foot Collins isn't much of an offensive threat, averaging 1.3 points, but Drew is counting on the 10-year veteran to provide a defensive presence.

Information from The Associated Press was used in this report.