INDIANAPOLIS -- As is usually the case when the Indiana Pacers win, Paul George provided plenty of offense.

But after Indiana's 103-98 victory Tuesday night against the Boston Celtics, George and the Pacers wanted to talk defense.

"Teams that stretch the floor have given us problems, so we had to guard to win this game," said George, who led all scorers with 25 points. "Our message tonight was, "Guard our guy."

Two George Hill free throws with 7:43 to play began a 6-0 Pacers run and the Celtics (39-28) never led again. It was only the fourth time in the past 30 games that Boston was held below 100 points.

Indiana (36-31) won the four-game season series with Boston 3-1.

Monta Ellis added 16 points, seven rebounds and six assists for the Pacers. Jordan Hill came off the bench for 15 points and Ian Mahinmi finished with 13 points and six rebounds.

The Pacers shot 46.4 percent from the field (39 of 84) and held Boston to 38.3 percent (36 of 94), including 8 of 32 from 3-point range.

Isaiah Thomas led the Celtics with 21 points, Jonas Jerebko had 17 and Jared Sullinger added 15 points and 11 rebounds. Marcus Smart scored 12 points.

"We have been more aggressive lately pressuring the ball," Mahinmi said when asked what fueled this Pacers' defensive effort. "That helped us slow the game down."

Indiana coach Frank Vogel enjoyed the effort.

"It wasn't pretty, but Boston is a tenacious defensive team," Vogel said. "I have a lot of respect for Brad Stevens' team. Offensively, we were able to build a lead, and Jordan Hill really benefitted from some great reads by Monta Ellis. Jordan is a great finisher around the rim."

Jordan Hill, like his coach, respects the Celtics and categorized this as a big victory.

"Boston is a great team that plays really good team ball," Jordan Hill said. "Down the stretch, we made some big shots and helped each other out on defense."

The Celtics took a 52-51 lead on Thomas' 3-pointer with 7:12 left in the third quarter. Thomas scored 16 points in the quarter, but an Ellis runner in the lane with 0.5 of a second left in the third gave Indiana a 71-70 advantage with 12 minutes remaining.

"We had those moments -- that stretch in the first half when we couldn't score and got down 10 -- but then we started playing great through the end of the third quarter," Stevens said. "We still were playing pretty well, but Monta Ellis gave them that shot to kind of tweak the momentum of the game, and then Indiana just dominated us in the paint after that.

"What I am discouraged about is that I think we can play with better purpose and give ourselves a better chance to win. And obviously, Jordan Hill loves playing against the Celtics. He has a great game against us every time."

The Celtics' Smart said the outcome can be described simply.

"We got a lot of good shots and had a lot of opportunities, but obviously, our shots were not falling," Smart said. "No one was cutting hard, and that allowed them to be right on top of us when we got the ball. We fell apart."

Led by Mahinmi's nine points, the Pacers grabbed a 43-39 halftime lead, outscoring the Celtics 23-19 during the second quarter.

Boston, which got 11 from Jerebko and nine from Smart, shot only 34.8 percent from the field (16 of 46) in the first half but outrebounded Indiana 26-24.

The Pacers trailed 20-13 in the first quarter but led 43-33 in the second quarter before the Celtics scored the final six points to pull to within four at intermission.

NOTES: The Celtics were without No. 3 scorer Jae Crowder (14.4 points), who has a right ankle sprain. ... F/C Kelly Olynyk (10.1) was out with a right shoulder sprain. ... Pacers G Ty Lawson is recovering from a sprained left foot and G/F C.J. Miles has an upper respiratory infection. ... Boston came in having won seven of its past 10 games. ... Indiana was 5-5 in its last 10 before facing Boston. ... Pacers F/G Paul George (23.3) was ranked 10th in NBA scoring and fourth in made 3-pointers (179). ... The game against the Celtics begins a sequence in which the Pacers play eight of nine in Bankers Life Fieldhouse. ... The Celtics lead the NBA in opponents' turnovers per game (16.7) and are second in opponents' 3-point field goal percentage (32.4) and second in steals per game (9.6). ... Indiana is fourth in steals per game (9.0) and sixth in opponents' turnovers per game (15.9) ... The Pacers won two of the first three meetings against the Celtics.