Maybe Bonner needed some time away from the team to get back into a good physical form. Even though he was focusing on his hamstring, the whole body gets to heal when you're not traveling or practicing. And if you aren't bound by the NBA schedule it's easier to do therapy and build strength. I'm not willing to say Bonner is better now than he was before, but he could be. He was moving awfully well out there. And while Butler offers a lot defensively off the ball, Bonner is much better there than people realize, especially on the ball.
Add in the fact that he's the only big who can shoot the three (even if you include Kyle and Rasual in there, Matt's the best by a long shot), and you have a real conundrum. Simmons may not be safe after all.