I ran through some rebounding numbers between Big Al, Lopez, Okafor, and Turner. Turner and Lopez have nearly the exact same contested defensive rebounding percentage at 33.4% and 33.3%, respectively, which would rank an impressive 5th and 6th among the 70 qualified centers (mpg>15 , GP>20). Big Al is ranked 17th at 29% while Okafor is 37th at 26.5%.
Here's where things start to get discouraging and reflect what we've all seen this season. Myles Turner ranks 64th out of 70 players in adjusted defensive chances rebounding percentage at 66.6% while Big Al is at 72.4% which is ranked 29th. Lopez doesn't rank much higher at 60th as he is posting 68.4%. Okafor bottoms out the group at 64.9% and ranks 66th out of 70.
What this shows is that Myles and Lopez have the ability to grab tough rebounds but they don't consistently go after the ball. In fact Myles also has a noticeably high number of deferred rebounds. While looking through just the team rebounding stats for the Pacers (http://on.nba.com/2lm0xhH) I noticed that Thad Young's average rebounding distance was 6.2 feet away from the basket which is a farther distance from even Paul George. So what we have is a young player in Turner who isn't nasty enough yet to consistently haul in rebounds although the potential is clearly there and a starting PF who is the same way.
The Pacers essentially have been playing 2 stretch bigs with similar games. Lopez would be another redundant player and Okafor is essentially a Big Al clone with worse rebounding numbers (though it my be a product of playing with Embiid at times who is a great rebounder). The Pacers severely need an athletic 4 with a great nose for the ball. The only player rumored to be available is Faried but trading a 1st round pick for him is risky as he's been inconsistent as well. I still really like Joel Bolomboy of the Jazz and think he'd be perfect for the role. If the Jazz would do it, I'd easily trade Big Al for Joel as they could use an established backup center.