CHICAGO - Willing to defer in the first two games, Paul Pierce took the initiative and the Boston Celtics seized control.

Pierce scored 24 points, Rajon Rondo added 20 and the defending champions beat the Chicago Bulls 107-86 on Thursday night to take a 2-1 lead in their first-round playoff series.

The teams split two dramatic games in Boston, but this one never really was in doubt. The Celtics led by 11 after one quarter and 22 at the half on their way to an easy win behind Pierce and Rondo. Particularly Pierce.

“We know what kind of team we are,” Pierce said. “The way we played tonight is the way we want to play.”

Now, Boston is in good shape heading into Game 4 Sunday even though the injured Kevin Garnett is wearing a suit instead of a uniform these days.

Rondo looked just fine for most of the night after spraining his right ankle in Game 2 and missing practice Tuesday. He hit eight of 15 shots, grabbed 11 rebounds, dished out six assists and collected five of Boston’s 16 steals, but afterward two teammates helped him down the hallway afterward. Even so, he insisted he’s OK.

“I didn’t want to limp in,” said Rondo, averaging 22.7 points, 9.7 assists and 10.7 rebounds in the series. “Everything’s fine with my ankle. The bottom of my foot was hurting. I’m fine.”

Pierce was more than fine.

He asserted himself after two rather quiet games, hitting his first six shots and going 9 of 15 overall. He was aggressive from the start, setting the tone as the Celtics pulled away early.

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“In Game 1 and 2, I was a little indecisive but I’m getting comfortable with what (the Bulls) want to do,” he said.

Ray Allen added 18 points after scoring 30 and hitting the tiebreaking 3-pointer to lift the Celtics to a 118-115 victory in Game 2 on Monday. Glen Davis chipped in 14 points, nine rebounds and six steals. And Boston hit 12 of 21 3-pointers — four by Pierce and three by Allen.

The Bulls covered the arena in rose petals in honor of Derrick Rose, who was named Rookie of the Year on Wednesday, but they couldn’t cover Pierce, Rondo or Allen. They couldn’t hang onto the ball. They couldn’t shoot, and they couldn’t hit their free throws.

It was that kind of night.

“The way we came out and played, the result is not a shock,” Chicago’s Ben Gordon said.

The Bulls committed 22 turnovers, shot 37.5 percent from the field and were 17-of-27 at the line after going 46-of-51 in the first two games.

Gordon scored 15 on 5-of-13 shooting after having 42 in Game 2, while John Salmons added 14.

Rose, who scored 36 as the Bulls won the opener in overtime, got outplayed for the second straight game by Rondo, finishing with nine points, seven turnovers and two assists.

“Hopefully, it will help us knowing that we have to work like this,” Rose said.

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Unlike the first two games, Pierce went right at the Bulls, scoring 13 in the first quarter as the Celtics grabbed a 32-21 lead. He looked like his usual self after shooting 40 percent while averaging a rather quiet 20.5 points in the first two games. That he didn’t assert himself earlier was a surprise, considering the man guarding him — Salmons — has a strained left groin.

Then again, the Celtics’ spacing was two tight in the first two games, limiting Pierce.

“I thought it was beautiful how he played,” coach Doc Rivers said.

For Rondo, it was simply more of the same.

He capped a nine-point first quarter that he capped with a 3, and Allen got going late in the half, when he followed a 3-pointer by Stephon Marbury with two of his own to make it 59-37.

It was an impressive showing by the Celtics, who are trying to make due without Garnett — out with a knee strain.

“I was thrilled with the way we played,” Rivers said.

Notes: Rivers said no date has been set for surgery on Leon Powe, who tore the anterior cruciate ligament and meniscus in his left knee in Game 2 and is done for the season. ... Commissioner David Stern said he’s been speaking to GM Danny Ainge “through the Celtics” after his mild heart attack last week. “There was a meeting last week in New York. Danny, that morning, he had been hospitalized and we were getting up-to-the-minute (reports).” ... The Bulls are the last team to eliminate the defending champions in the first round, after sweeping Miami in 2007.

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