ATLANTA — The series may be four games old and neither team owns a critical victory but right now the Atlanta Hawks seem to have the Celtics back on their heels.

After two momentum-filled wins at Philips Arena, it is the Hawks who probably can’t wait to get the Celtics back on the floor in Game Five tomorrow night at TD Banknorth Garden.

The Celtics whipped the Hawks twice in Boston but several cracks in the NBA’s best regular-season team have opened during the last two games here. Whether the Hawks can transfer their inspired play to New England remains to be seen.

“It’s win or go home,” said Atlanta guard Mike Bibby. “We have not been playing good on the road, but we have been playing together on both ends (of the court) here at home. When we do that, we have good games.”

Boston’s Ray Allen said the events of the last two games have put the Celtics’ into crisis mode.

“We always said a series starts when you win on the other team’s floor,” said Allen. “There’s a serious nature of business we have to attend to now.”

Paul Pierce said the difference in the Celtics’ two wins and two losses clearly lies on the defensive end of the floor. When Boston keeps Atlanta’s stars in control, it can dominate. If not, all bets are off.

“You definitely want to be in better position going home, but they played great, man,” said Pierce. “Joe Johnson, Josh Smith, Al Horford, Mike Bibby — they really came with it these last two games on their homecourt where they’re comfortable. We have to figure out a way to slow them down.”

Shot clock OK

The good news is the shot clock did not break down last night. The teams played without the clock for the majority of the second half and while the Celtics had little to say about the malfunction’s effects on their play just after Game Three, they’ve had plenty to say in the last two days.

The best story came from several players who said they knew something was amiss on one possession when Rajon Rondo dribbled over the midcourt line and the public-address announcer called out “10 seconds.” Rivers said he also had an issue with the cadence the P.A. man called out the last five seconds. “For us it was 5-4-3-2-1. For them it was a little slower,” he said with a laugh.

When the clock broke down during halftime, Rivers said he initially told lead official Bennett Salvatore that he didn’t want to continue the game. Teams are supposed to have back-up clocks on hand but the Hawks could not operate those either.

“I didn’t want to play. I told Bennett I didn’t want to play. Go get a clock,” said Rivers. “I didn’t want the Hawks’ announcer to call it out. I wasn’t born yesterday.”

kmcnamar@projo.com