In Miami, the Heat's 78-75 loss left their Eastern Conference semi-final series tied at 1-1.
Bosh has been ruled him out "indefinitely" after picking up an abdominal strain in Game One on Sunday and questions are being asked about how effective the Heat can be without one of their key components.
With the Heat holding a 38-33 lead at halftime, however, there was little indication of the turnaround that was to put last year's runners-up in trouble.
Indiana dominated the third quarter, outscoring Miami 28-14 and grabbing a nine-point advantage heading into the fourth.
With Bosh on the sidelines it was left to LeBron James and Dwyane Wade to carry the Heat. The duo came up with 21 of Miami's 23 fourth-quarter points but James missed two free throws and Wade came up short with Miami three down and less than 10 seconds on the clock.
Miami failed to score in the final two minutes and 41 seconds of the game and their last chance to tie the score ended with Mario Chalmers' three-point effort hit the rim.
James led Miami with 28 points and nine rebounds and Wade put up 24 points and made six rebounds.
David West top scored for the Pacers with 16 points but was quick to put the victory in context.
"We have nothing to celebrate yet, we have just won one game in the series," he told TNT television.
"I thought we were more aggressive defensively and we were able to maintain our composure, early on we were able to stop them doing a couple of things they like to do and that carried over through the game," said West.
The series moves to Indianapolis for Game Three on Thursday.
In San Antonio, the Spurs ended their week-long break with a 108-92 rout of the Clippers.
Tim Duncan looked fresh, the 36-year-old recording 26 points and 10 rebounds as the Spurs took advantage of a weary Los Angeles team who just concluded a physical seven-game series against Memphis.
"We just attacked the basket as much as possible and tried to take some of their aggressiveness away," said Duncan, who helped his team win their 15th consecutive game going back to the regular season action.
"It's the play-offs, it's going to be physical. Especially with the series they just got out of."
The Clippers, playing in the second round for the first time since 2006, were still in the picture until a 14-3 run in the third quarter put San Antonio up by 19.
Blake Griffin had 15 points and nine rebounds and looked to have shaken off the effects of a knee injury suffered in the first round. Chris Paul made just three of 13 shots for the Clippers and had six points and 10 assists.
Manu Ginobili added 22 for the Spurs.