Boston — The Hawks have already done the unthinkable by drawing even at two games each in their playoff series against Boston.

Now they have to do the improbable and win on the road in a hostile environment with everything on the line for both teams.

Having tasted the prickly nature of the fans at TD Banknorth Garden in blowout losses to the Celtics in Games 1 and 2, the Hawks know that Wednesday's Game 5 will be unlike anything they've experienced this season.

"This series boils down to us getting a road victory, plain and simple," said Hawks captain Joe Johnson, the Game 4 hero after his 35-point effort. "We've got to buckle down, man, defensively and just go out there and beat these guys.

"We know it's going to be tough. But we think it can be done."

Why would the Hawks think otherwise?

They have the momentum.

They are without the pressure of expectations.

They are playing on younger legs at a time when that pays huge dividends.

Whether it pays off depends on the Hawks playing as well on the road as they did at home.

"It's going to be tough," said point guard Mike Bibby, the Hawks' most experienced player. "But there's no pressure on us. We've seen what it's like. The first two games were really about just getting a feel for a lot of the guys and seeing how we had to play them.

"But I keep telling these guys that [playoff] basketball is a game of momentum and confidence. And right now our confidence and momentum are good."

Good doesn't begin to describe the way the Hawks have played in the last eight quarters. They've dominated the Celtics in nearly every facet. And even when they have struggled — they trailed by double digits twice in Monday's Game 4 win at Philips Arena — they have found ways to come back.

Doing the same thing on the road is the only remaining hurdle.

"It's going to be a real greasy atmosphere," Josh Childress said. "We know it's going to a nasty place. They'll be booing us from the warm-ups until the end of the game. But we're going to embrace that. We want to prove to people that we can win on the road and that we not only belong here [in the playoffs], but also that we can compete with anybody."

The Celtics aren't just anybody.

They haven't lost three consecutive games all season; they lost two in a row on three separate occasions.

Pegged for a spot in the Eastern Conference finals since blockbuster trades last summer that brought All-Stars Kevin Garnett and Ray Allen to town, these sudden struggles with the lowly Hawks — who slid into the playoffs with a 37-45 record — weren't supposed to happen.

Yet the Celtics now must defend their home court with their season hanging in the balance.

"We didn't want this to happen," said reserve Celtics point guard Sam Cassell. "But we have our work cut out for us now. We're going to have to figure out a way to score more points [in Game 5]. And we have to find our chemistry quickly. This game isn't going to be easy just because we're at home. The Hawks have confidence. And they think they can beat us."

The Hawks have won just 12 of their 43 road games, including Games 1 and 2, on the road this season.

"We've struggled but when we were coming down the stretch [of the regular season] and had to get some key games like at Washington, at Philadelphia and New York, we got it done," Hawks coach Mike Woodson said. "It's not like these guys aren't capable of winning on the road. We just have to make sure our mind-set is to play 48 minutes, defending, rebounding and sharing the ball offensively.

"We do that ... and who knows what will happen."