Mike Dunleavy and Brandon Rush share a vital role with the Pacers.

They both average 30 minutes per game and have become interchangeable at shooting guard in Jim O’Brien’s starting lineup.

“You have to always be prepared because you never know when you’ll be starting.” Rush told RealGM.

Since Rush returned from a five-game suspension to begin the season, the third-year guard has started eight times. Dunleavy has been on the floor for the opening tip 20 times, including 15 starts since Rush returned to the active roster.

With the pair switching roles so often, I wondered how much of a warning O’Brien gives them heading into each game.

“He’ll usually tell us in shootaround the day before, but it doesn’t really matter,” Dunleavy said.

Just to be sure, I asked Rush the same question. He corroborated with Dunleavy’s answer.

“We’ll know the day before the game or sometimes during a morning shootaround,” Rush said.

They both started against Chicago on Dec. 13 because Danny Granger sat out with an injury. I’ve removed that game from any statistical comparison.

When Dunleavy starts over Rush, Indiana is 10-9. As would be expected he averages more points (12.8 to 10.3), rebounds (5.8 to 4.0) and minutes (32.4 to 24.1) when he’s on the floor first. However, he shoots the ball at a 53.3% clip when coming off the bench as opposed to just 43.2% as a starter.

The Pacers are 3-4 with Rush opening the curtain and his numbers fall in line with what you’d expect as well. His points (14.5 to 11.1) and rebounds (4.1 to 3.6) are greater in his starts, but his minutes are more consistent than Dunleavy’s (34.1 to 28.0). Unlike Mike, he shoots better (47.9% to 44.4%) as a starter.

“No, not really,” Dunleavy said when asked if he could predict when he’ll start/sit. “I think both of us are always prepared to do whatever is asked of us. I don’t think it’s a big deal for either one of us because we’re both comfortable in both situations.”

The obvious answer, despite what Dunleavy says, is that O’Brien makes his decision at least partly based on the opposition. Rush, the superior defensive player, has started against the Heat, Celtics and Lakers (twice).

“It’s always fun to see who I’ll be guarding,” he said.

Their split offensive statistics would be a good indicator of who does a better job as a starter, but there aren’t any glaring numbers to pick out for either player.

Using team statistics in this case can be tricky as well, especially given the fact that often times Dunleavy and Rush finish games with comparable minutes regardless of who starts.

Still, the numbers actually make a decent argument for Dunleavy’s case as the permanent option.

The Pacers average 94.8 possessions for 48 minutes with Dunleavy as the starter and just 92.4 with Rush. You don’t have to have seen more than a handful of their games to realize why this is the case.

Dunleavy gets lost on the defensive end a considerable amount and was abused by Allen in Boston. After leaving him open for a three, Dunleavy closed out too hard a few possessions later and Allen drove right past him. Later, Allen changed directions on a fast break and Dunleavy was left confused as his man scored an easy lay-up.

Rush quite simply puts up more resistance.

The game’s pace might be slower when Rush establishes a presence early, but Indiana’s offensive and defensive ratings side with Dunleavy.

Indiana has an offensive rating of 105.7 in Dunleavy’s starts and 102.5 in Rush’s.

You’d expect the opposite to be true of their defensive rating, but the Pacers have a 103.5 defensive rating with Dunleavy as the No. 1 two-guard and a 104.3 rating with Rush. It will be interesting to see if this remains the case as the season progresses.

O’Brien’s claim that the pair are interchangeable seems correct, but there is one factor that must be considered as well: How long will Dunleavy be with the Pacers?

His contract expires after the season and he could be an attractive option for a contender around February’s trade deadline. With that said, if the Pacers remain in the hunt to end their lengthy playoff drought, I’d be surprised to see them move Dunleavy without getting something considerable in return.

Even if Indiana holds onto him for the remainder of the season, he could sign elsewhere as a free agent this coming summer. O’Brien said earlier this month that he hopes president Larry Bird and general manager David Morway re-sign Dunleavy, but Rush is still the likely future at the position.

“It’s a long way away and we’re trying to get through this season here, but obviously I love Indiana,” Dunleavy said when asked about O’Brien’s comments. “I love being a part of this team, but there’s a lot of stuff going on – collective bargaining and free agency – so it’s definitely hard to predict.”

Dunleavy arrived in Indiana nearly four years ago when the Pacers were just starting their lengthy rebuilding process. It appears as though they are finally starting to see the fruits of their labor.

“Yeah, we’re definitely heading in the right direction. They have players here now that they want to have here for a long time,” he said. “When I first came here they were kind of cleaning house, so it’s nice to be a part of the chance and hopefully I can see it through.”

Andrew Perna is Deputy Editor of RealGM.com. Please feel free to contact him with comments or questions via e-mail: Andrew.Perna@RealGM.com. You can also follow Andrew on Twitter: APerna7.