WALTHAM, Mass. — Long after practice ended, Ray Allen was still on the court firing up jumpers.

He was even making most of them.

That overtime work yesterday showed that, like his Boston Celtics teammates, he had plenty of energy left after two intense seven-game series. And the usually smooth shooter was regaining his rhythm.

Whether the Pistons still have theirs after a six-day layoff will become evident in today's opener of the Eastern Conference finals.

"I would rather have the rhythm" of regular competition than extra rest, Allen said, "because (with) the rhythm you don't have to guess from one day to the next" how you'll play.

Boston has played three games since Detroit won its conference semifinal in five games against Orlando last Tuesday. The Celtics advanced with a 97-92 victory over Cleveland on Sunday in which Paul Pierce scored 41 points. Allen had just four and averaged only 9.3 points on 32.8 percent shooting in the series, far below his regular-season performance.

If he starts scoring again, he would give the Celtics their usual three main scoring options, joining Kevin Garnett and Pierce, to go against a Pistons team that has a much more balanced offense than the Cavaliers, who lost Sunday despite 45 points from LeBron James, and Atlanta, Boston's first-round opponent.

"It's the exact opposite," Celtics coach Doc Rivers said. "You go from Cleveland and Atlanta in a lot of ways with Joe Johnson, where you focus on double-teaming, to playing a team that all the guys in the starting lineup are capable of having good nights."

The matchup with Detroit is what Rivers and many others expected.

Both are deep teams with outstanding defenses. The Celtics had the NBA's best record (66-16), earning home-court advantage throughout the playoffs, and the Pistons were second best (59-23). The Celtics have plenty of players with playoff experience, though not as teammates, and the Pistons are in the conference finals for the sixth straight season.

Chauncey Billups, Richard Hamilton and Tayshaun Prince have been on all of those teams. Rasheed Wallace is in his fifth year with the Pistons. But they last won the NBA title in 2004, then lost to San Antonio the next year.

Pierce, Garnett and Allen are each in the conference finals for only the second time in their careers.

"I think we probably will be the underdog," Pierce said, "knowing that Detroit has been there. They won a championship with this group and are used to going to the Eastern Conference finals and this is just our first trip."

Still, the Pistons are hungry to get back to the finals for the first time since 2005.

"It's only been three years, but it seems like forever," Hamilton said. "We feel ... we haven't been there in a long time. So we want to do everything possible to get right back to where we were at."

Boston was 8-0 at home but 0-6 on the road in the first two rounds. The Pistons have three road wins in this postseason.