TLANTA - The first half of last night's game against the Hawks left Erick Strickland ''dumbfounded,'' Antoine Walker defensive, and Paul Pierce asking, ''What are we doing out here?''

For the first two quarters, however, it was all about what the Celtics didn't do (rebound, stop the Hawks from shooting 63.6 percent) and what they didn't have (the intensity necessary to win on the road). The Celtics knew they came out flat. They just couldn't figure out why.

The Celtics have three days to sleuth out an explanation for the slow start that led to a 112-103 loss before 10,563 at Philips Arena. On Wednesday, the Hawks (3-7) will be in Boston for a rematch, with the Celtics (5-3) determined not to squander another opportunity against an Eastern Conference team. It's early in the season, and they don't want to make the same mistake twice. They don't want to fall behind by 17 points at halftime and a game-high 20 early in the third, then spend the remainder of the contest playing a frustrating game of catch-up.