Indiana found its bearing in the paint after losing its composure late against San Antonio.
"We just had to calm down," Indiana coach Nate McMillan said. "We had get back to calm and execute out there."
The Pacers won their fourth straight, moving into a fifth-place tie with the Philadelphia 76ers in the Eastern Conference.
"It's all about being competitive and executing and you've got to do it for more of the 48 minutes than your opponent," San Antonio coach Gregg Popovich said. "We didn't do anything in the second quarter to help ourselves. In the second half, we competed our (butts) off (and) did a really good job, but little things got us, execution-wise."
San Antonio trailed 84-69 with 4 1/2 minutes left in the third quarter before rallying. The Spurs went ahead 102-98 with 6:44 remaining in the game, fueled by a pair of 3-pointers each from Mills and Lonnie Walker IV and an emphatic slam by Walker.
Walker finished with 10 points.
Domantas Sabonis had nine of his 14 points in the final quarter.
Indiana was without Victor Oladipo, who suffered swelling in his right knee following the team's morning shootaround. McMillan said it's too early to tell how long Oladipo will be out.
"He's a huge piece to what we do," Brogdon said of Oladipo. "But this is a locker room full of confident guys. When one person goes out, the beauty of this team is we adapt, and we have guys that can step up and fill in and continue to play good ball."
It took some adjustments early, though.
The Spurs made their first four shots, including back-to-back 3-pointers by Lyles and Bryn Forbes, in racing to a 10-0 lead.
"They are a couple of players down right now, but you can't expect to come to San Antonio and get an easy win," Indiana center Myles Turner said. "Every time I've played here since I've been in the league it's been a tough time."
The Pacers responded with their own hot streak on 3s. Indiana was 9 for 14 on 3-pointers in the second quarter.
Brogdon's driving, reverse layup gave the Pacers their first lead at 48-46 with 6:21 remaining in the first half. Indiana extended its lead to 61-51 on one of Doug McDermott's four 3-pointers.
McDermott had 14 points, going 4 of 5 on 3s.
Pacers: Oladipo missed more than a full calendar year after rupturing a quad tendon in his right knee on Jan. 24, 2019. McMillan did not address whether the team was being cautious with Oladipo because of the previous injury. ... Indiana has won three straight at San Antonio.
Spurs: Aldridge is expected to return to the lineup Friday at Brooklyn after skipping Tuesday's game at Charlotte, Popovich said. ... Poeltl sprained his right MCL during the first quarter of San Antonio's 114-113 victory over Orlando on Saturday. ... Drew Eubanks became the first player on a two-way contract to start for the Spurs. Eubanks finished with three points and two rebounds in 13 minutes. ... Rudy Gay was issued a technical foul with 3:26 remaining in the third quarter after tossing the ball toward Marc Davis after the official had called a foul on the Spurs forward.
Walker electrified the crowd with his dunk that tied the game at 96 with 7:51 remaining.
Walker has earned a regular role with the Spurs by being aggressive on both ends after spending most of the first two months of the season on the bench.
"You've got to have that mentality of just being a killer," Walker said of his dunk. "Trying to dominate and do what you can. If I have a full head of steam, and no one's really on me, nine times out of 10 I can jump with the best of them. So, good luck trying to block me."