Acquiring Ray Allen and Kevin Garnett in the offseason has helped give Boston (46-12) the league's best record, but it hopes to have picked up the last piece of a championship puzzle by signing Cassell to a contract Tuesday. The veteran point guard is headed to Baltimore to attend the funeral of a family member and won't be available Wednesday, but he is expected to be play Friday against Chicago.

The 38-year-old Cassell averaged 12.8 points this season for the Los Angeles Clippers before negotiating his long-rumored exit. His playoff experience is expected to serve the Celtics well as they make a push for their first title since 1985-86.

Detroit (44-16), three games behind Boston in the East, may be the Celtics' biggest obstacle to a championship. The Pistons and Celtics rank 1-2 in the league in scoring defense, allowing 90.2 and 90.6 points per game, respectively.

Boston and Detroit are meeting for the final time in the regular season. Both teams have a win on the road in the season series.

"People are expecting that to be the Eastern Conference finals matchup," Garnett said. "It should be a fun game."

Knowing much of their title hopes rest on Garnett's shoulders, the Celtics rested him for nine games at midseason when he was nursing an abdominal strain. The 6-foot-11 forward has played in eight games since returning, and his last contest was perhaps his best over that stretch.

Garnett had 20 points and 16 rebounds to lead Boston to its fifth straight win, 98-88 over Atlanta on Sunday night.

"He's all the way back," Celtics forward Paul Pierce said. "When he's going to the basket, inside and outside, dominating the rebounds: That's the Kevin Garnett I like to see."

Garnett is averaging 20.5 points and 8.5 rebounds in two games versus the Pistons this season.

Detroit was beginning its worst stretch of the season when it last played Boston, losing 92-85 on Jan. 5. The Pistons went on to lose five of their next eight games.

Since then, however, Detroit has won 15 of its last 18 and has the league's second-best record. The Pistons came home from a 3-1 road trip to beat Seattle 100-97 on Tuesday night.

Detroit will now play two straight on the road, where it is an Eastern Conference-best 21-11. The Pistons have won four straight and seven of their last eight in Boston, including an 87-85 victory on Dec. 19.

Chauncey Billups had a game-high 28 points and eight assists for Detroit in that game. He had 20 points and nine assists versus the SuperSonics, reaching 20 points or more for the third straight contest.

Billups will match up with Celtics point guard Rajon Rondo, who will end up splitting time with Cassell.

Detroit made its own late-season acquisition Tuesday, signing center Theo Ratliff. The 13-year veteran signed a free-agent deal with the Pistons - the team he started his career with in 1995 - after being released Friday by Minnesota to pursue opportunities with a contender.

"It's great to be back," Ratliff said. "I feel like I'm home again."

Ratliff will provide depth in the frontcourt behind Rasheed Wallace and Antonio McDyess. Coach Flip Saunders said that Ratliff could play Wednesday.