Paul Pierce has been battling a sprained knee ligament, but he officially entered the Boston Celtics Eastern Conference semifinal series with the 76ers as a major factor in Wednesday's 107-91 win at the Wells Fargo Center.

Pierce had 24 points, 12 rebounds and four assists in helping the Celtics take a 2-1 advantage in this best-of-seven series.

No, the shooting numbers still weren't great for Boston's 14-year veteran forward and 10-time all-star from the University of Kansas. Pierce shot 6 of 17 but from where he started to where he ended, he was a major factor.

Kevin Garnett, who had another monster game with 27 points and 13 rebounds, and Rajon Rondo, who added 23 points and 14 assists, will justifiably earn the main headlines, but the grit and overall production of Pierce can't be discounted.

He began the game pretty much the way he played the first two in this series - not very impressively.

Pierce, who shot a combined 5 for 20 as the teams split the first two games in Boston, began Wednesday's contest by missing his first six shots from the field. Yet he ended with nine points in the first quarter, keeping the Celtics competitive before they could truly find their rhythm.

Rarely does someone shoot 2 for 8 from the field in the first 12 minutes and make such an impact.

The Sixers won the first quarter 33-28. Without Pierce, things would have been much worse for Boston.

Pierce scored the Celtics final seven points of the quarter, including two driving dunks.

"I wanted to be aggressive regardless," Pierce said. "When I'm limited to 7 to 9 shots in a game, that isn't me, and I have to be aggressive in everything I do."

Pierce is known for coming up strong in the big games. He was the 2008 playoff MVP, leading the Celtics to the NBA title.

Pierce first suffered the knee injury in Game 4 of the Celtics opening-round win over the Atlanta Hawks, yet he insists that isn't a detriment.

"I feel fine," he said.

Leading 60-49 at halftime, the Celtics broke the game open with a 29-17 third quarter. Pierce was perfect in the third period, scoring 10 points while going 2 for 2 from the field, 1 of 1 from beyond the arc and hitting all five free throws.

"We came out in the third quarter and established things early," Pierce said. "We haven't put together great third quarters in this series and I thought that was key, especially on the road."

His point regarding the third quarter was well-made. In Game 2's 82-81 loss, Boston was outscored by the Sixers, 21-11, in the third quarter.

Pierce may have said he was fine, but even when he's 100 percent, he isn't exactly fleet of foot.

"Paul is just a grinder," Celtics coach Doc Rivers said. "You look at him at times and wonder how this guy gets it done."

He doesn't have much flash to his game.

"With him, you could see early on he missed two layups and had no lift and then all of a sudden he dunked the ball down the lane and got five offensive rebounds," Rivers said. "Guys like Paul and Kobe (Bryant), they have something in their minds that makes them who they are."

Contact Marc Narducci at 856-779-3225, mnarducci@phillynews.com or @sjnard on Twitter.