Waltham, Mass. ? A day after grumbling about being used as a decoy with the game on the line, Paul Pierce said he’s no longer upset that Celtics coach Jim O’Brien went elsewhere for the potential series-clinching shot in the final minute of Boston’s playoff loss to Philadelphia.

“It was the heat of the moment,” Pierce said Monday. “I was upset. We lost the game. That’s about it.”

The 76ers beat Boston, 108-103, Sunday in Game 3 of the best-of-five series.

The Celtics lead 2-1, with Game 4 on Wednesday.

Pierce was already upset with 34 seconds left, when the Celtics returned to the floor after a timeout trailing 104-103. O’Brien had just called a pick-and-roll involving Rodney Rogers and Kenny Anderson.

Whatever play was called, Antoine Walker wound up missing a three-pointer and Allen Iverson got the rebound. Pierce had a chance to tie it later, but he missed an off-balance shot from 27 feet with 2.5 seconds left.

Boston talk radio hosts on Monday compared Pierce to Scottie Pippen, who refused to go back into a game for the Chicago Bulls in the 1994 Eastern Conference semifinals when coach Phil Jackson drew up a play for Toni Kukoc with 1.8 seconds left.

With Pippen pouting on the bench, Kukoc hit the shot to win the game.

But Pierce’s reaction was very different from that, and O’Brien was willing to write it off as competitiveness.

“I thought the call was the right one; Paul might not have thought so. He and I have good communication. He’s confident I’ll make the right call,” O’Brien said. “Sometimes you have go-to guys you have to use as decoys, knowing the other team is absolutely not going to let them get the basketball. We have to trust that when they’re used as decoys, the other guys will step up and make the shots.”

Pierce, who had 29 points Sunday, scored more than anyone else in the NBA during the regular season, including a league-high total of 552 points in the fourth quarter.

Pierce and Walker accounted for half of the Celtics’ points during the regular season, a ratio that has gone up to 54 percent during the playoffs.

“Paul knows, at the end of the game, that the ball’s either going to him or Antoine. So does (Philadelphia coach) Larry Brown. So does the entire 76ers team,” O’Brien said.

“We have two guys that are the cornerstone of our franchise: Antoine and Paul. They want the basketball at key times. I want them to have the basketball at key times. But sometimes you have to use Paul and Antoine as decoys. They had two guys guarding Paul. They weren’t going to let him get the basketball. I knew that at the beginning of the series.”

O’Brien said he had called six of the previous seven plays for Pierce and thought it was time to mix things up.

“They’re too good of a team to just let me and Paul score,” Walker said. “We’ve got to run plays to confuse them and mix things up.”

Guard Eric Snow said the 76ers didn’t know if Pierce was a decoy or if he was just too well-covered to get the ball for the game-winning shot.

O’Brien “probably felt that we expected Paul to shoot. … (Pierce) probably wanted coach to say, ‘Don’t nobody shoot but Paul, unless you’re wide open,”‘ Snow said. “Walker had made seven threes. Rodney Rogers had just hit a couple, so take your pick. They all can shoot it.”