The Celtics' home-court advantage has produced an overtime loss and last night's last-gasp, 118-115 victory over the Chicago Bulls. That would not seem to be an encouraging sign for Games 3 (Thursday) and 4 (Sunday) in Chicago.

Or, maybe it is, according to captain Paul Pierce.

"I think we feel very confident," Pierce said. "We feel like we haven't played good basketball yet. I feel like this is pretty much our 'C' game. We've given up 100 points two games in a row, allowed people to shoot 49, 50 percent. I think our best is yet to come in this series."

But it is clear the Celtics' playoff run is either going to be shorter or rockier than last season, judging by the loss of Leon Powe (left knee) and the fact that they had to make a dramatic rally from a 5-point deficit to pull this one out.

The Celtics were on top of their game at the start, Rajon Rondo jetting his way to a triple-double by early in the third quar ter. And they closed things out with some excellent execution, Ray Allen breaking out of a shooting slump to score 28 points in the second half, including the deciding 3-pointer with two seconds remaining.

Until that Allen launch over Joakim Noah, though, the Bulls had matched the Celtics step for step and basket for basket for 95 minutes, 58 seconds. Ben Gordon scored 42 points although the Bulls did not counter the Celtics' rebounding intensity; Boston had a 50-36 rebounding edge, scoring 32 points off 21 offensive boards.

The win boosted the spirits of the Celtics, who Thursday morning had absorbed the news that Kevin Garnett (right knee) would be out for the playoffs and that president of basketball operations Danny Ainge had sustained a mild heart attack.

That was followed two days later by an upset loss in the playoff opener.

Ainge attended yesterday morning's shootaround and Garnett joined his teammates on the bench for the entire contest. But after taking a 12-point first-quarter lead, the Celtics lost Powe to injury and faced a scare as Rondo went down with a sprained ankle.

"I pray that Danny Ainge didn't watch this game," coach Doc Rivers said. "What a great shot by Ray. We really needed somebody.

"At halftime, you've got Rondo landing in the training room and Leon injured and guys in foul trouble. And, you know, basically, at halftime all I said was, I needed a volunteer. And it was Ray Allen."

Savior was more like it.

Rondo (19 points, 12 rebounds, 16 assists) healed and outdueled Derrick Rose. Glen Davis, who played a total of 137 minutes in last year's playoffs, followed an 18-point Game 1 with 26 points and 9 rebounds. Both Kendrick Perkins and Rondo grabbed seven offensive rebounds. But Pierce had another off night, with 18 points on 19 field goal attempts. And the Celtic bench produced 9 points.

The outcome was in doubt, and the fact that the Celtics have had to go to the wire at home raises questions about their ability to repeat as NBA champions.

After the Bulls took a 109-104 lead, the Celtics closed with a 14-6 run, capped by a three by Allen, who had been held to 4 points in Game 1 and was 2 for 16 from the field in the opening six quarters of the series.

The Celtics had taken a 104-101 lead on Pierce's second-chancer with 4:35 remaining. But Rose scored on a follow, then Gordon hit two threes after the Bulls blocked Pierce shots, the Celtics calling timeout with a 5-point deficit with 3:11 left.

The Celtics failed to score on their next possession, but they capitalized on a Gordon misfire with a Davis layup, igniting an 8-2 run.

Rondo converted off a steal to cut the deficit to 109-108 with 1:54 remaining. Gordon scored out of a timeout, but Davis hit two foul shots and Rondo hit a jumper over Noah with :02 on the shot clock for a 112-111 edge with 1:01 remaining.

Gordon restored the Bulls lead, then Allen converted a second-chance three after Rondo controlled a tipped offensive rebound for a 115-113 lead with 25.3 seconds to go. Gordon's jumper out of a 20-second timeout tied it, and the Celtics called timeout with 12.3 remaining.

Allen then fired an off-balance shot off a double pick, Noah stepping out and nearly blocking the attempt.

"I actually thought Ray was going to be wide open," Rivers said. "And when he got it, Noah came out of nowhere - that was a hell of a recovery by him."

And quite a recovery by the Celtics.

© Copyright 2009 Globe Newspaper Company.