The Boston Celtics played home game after home game to begin the season, but the March road trip loomed like a gallows in the distance, ready and waiting to execute the Celtics in one eight-games-in-13-days stretch. Doc Rivers claimed not to be worried. The road would galvanize his squad, he said, mold it into a cohesive unit, tie it closer at the seams.

And here the Celtics have arrived at the last day of the trip — rather than becoming shark food, they have a chance tonight to surpass the Philadelphia 76ers for first place in the Atlantic Division and the accompanying No. 4 seed in the playoffs. Just last night against the Bucks, the Celtics strolled into Milwaukee to meet a steaming-hot crew that had won six straight, and waltzed away with a win, perhaps the season’s most satisfying team effort.

The Celtics offense carried it in the first half, and the defense allowed just 29 percent shooting in the final two quarters. Avery Bradley hounded Brandon Jennings, Greg Stiemsma blocked or stole everything in sight and each Celtic (sans Ray Allen, whose heat seekers misfired several times) excelled in his defined role.

Paul Pierce scored aplenty. Mickael Pietrus drilled outside shots and provided dogged defense. Rondo waved his wand and supplied a double-double. Kevin Garnett, as he tends to do, impacted every facet of the game. Brandon Bass provided instant offense when it was necessary. Keyon Dooling emerged from a season-long nap to drill all four of his shots. It wasn’t just that each Celtic contributed to the victory — it was how each Celtic contributed to the victory, exactly the way Doc Rivers would have designed it, with each man sticking to his niche.

This was what Danny Ainge envisioned when he built the Celtics this summer, mixing a bunch of grizzled veterans with hard-working youths on the bench, forming what he hoped would become a basketball assembly line where each Celtic concentrated on his strengths. There would be no bitching about roles this season, Ainge hoped, because he sought only players who would be comfortable working in the shadows. And finally — thanks to the insanity of this lockout- and injury-infested season, which allowed Stiemsma to dip his feet into the water and become comfortable with the temperature earlier in the season, which let Bradley run the show and build confidence while Rondo nursed an early-season injury, which forced Rivers to move Garnett to center and Bass into the starting lineup — the Celtics look like they might be turning into the well-balanced, if not uber-talented, machine Ainge thought he had created.

These Celtics won’t overwhelm anybody with athleticism, not anymore, but on days like yesterday, when each step on the assembly line functions as it should, they can still outclass anyone. This is what makes them the token “lower-seeded team nobody wants to play” — their occasional ability to function better as a team than their opponent, their ability to think the game and work at it and outlast teams with more athletic ability. The Celtics aren’t as talented as the Miami Heat or Chicago Bulls, but they have four stars who can erupt on any given night, one star, Kevin Garnett, who has returned into being a pillar of consistency, and several reserves who understand their limitations and can function as small parts of a larger whole.

The Celtics aren’t the favorites. They won’t ever be again, not with this nucleus, at least. But they’re becoming the team Ainge envisioned, a team defined by players who won’t stray from their own lane. And that’s what makes them scary, no matter how many miles the odometer has registered.