"Everything is starting to come together," Pierce said after falling two points short of his career high. "We're feeling good about ourselves. We're confident. We never felt that we were going to lose this game even with Antoine (Walker) out and Randy (Brown) hurt.
"I could see it in everybody's eyes."
The Celtics were without Walker, who is attending his grandmother's funeral in Chicago on Saturday, and Brown, who hyperextended his left knee in a win at Indiana on Wednesday.
It didn't matter.
Eric Williams scored 17, Bryant Stith had 14 and Vitaly Potapenko added 13 points and 10 rebounds to help make up for Walker's absence.
Boston took control of the game with a 26-6 run midway through the second quarter.
"I think we responded well to him being out," Pierce said, referring to Walker. "That brought us closer together. I don't think Detroit thought we would come out so hard without Antoine, they thought it would be a little bit easy."
The Celtics are 8-4 since Jim O'Brien replaced Rick Pitino on Jan. 8.
"They're taking pride in their defense," O'Brien said. "We've limited our rotations. The guys that are playing are the guys that are our toughest defensive players."
Detroit's Jerry Stackhouse scored 40 points, Chucky Atkins had 14 and reserve Mateen Cleaves added 13 points.
"Other guys need to start making something happen and stop looking to Jerry to make all the plays," Atkins said.
The Pistons have lost eight straight at home since beating Boston on Dec. 26. It's their worst streak at The Palace since losing 10 consecutive during the 1993-94 season.
"If we are not focused and playing real hard, we are not very good" Detroit coach George Irvine said.
Stackhouse tied a team record with 20 points in the first quarter, but the game was tied at 29.
Pierce, who scored a career-best 42 points against Minnesota on Jan. 15, scored 15 points during Boston's decisive run, which took the Celtics from a 38-32 deficit to a 58-44 advantage.
The Celtics went on a similar spurt when they beat Detroit on Monday at home. A 38-12 run helped them turn a 16-point deficit late into the third quarter into a 99-87 win.
Boston led 64-52 at halftime, which marked the most points the Pistons have given up in a half this season. The Celtics led 82-72 after three quarters.
Detroit cut its deficit to 97-91 with 2:02 left, but could not get closer.
Notes: O'Brien said he and a couple of coaches and players will attend Walker's grandmother's funeral. ... Walker is expected to miss Sunday's game against Cleveland and Monday's against Toronto. ... Detroit activated Eric Montross and put Billy Owens (back spasms) on the injured list. ... Boston won the season series over Detroit 3-1. ... Stackhouse has scored 40 or more five times this season.