Both centerfielders who also both got their shot during pennant races, but a huge difference in performance. Make no mistake, Ellsbury in 2007 and Bradley in 2013 were/are called up to help the club after an injury took out the starting centerfielder--Ellsbury this year, Crisp in 2007.
Right now Bradley has played 29 games with 78 at bats and an OPS of .540. At the same age, 23, in 2007 Ellsbury played 33 games with 118 at bats and an OPS of .902. Both, I agree are/were small sizes, but at the same time they are no doubt indicators for the front office. Thus Ellsbury returned to Boston in 2008 as a regular, albeit one who moved around in the outfield because Crisp was still in Boston.
With Ellsbury about to be a very expensive free agent, this is a golden opportunity for Bradley, especially since we already know he is a good outfielder. Not much of a basestealer, he does need to show he can hit, and so far he hasn't. Last night's game thread had at least two complaining Farrell should have started Bradley in CF against a righty starter, but they ignored the fact that Carp and Nava are both much hitters against righties. Moreover, the Sox are still in a race to get the home field advantage against Detroit and Oakland, so Farrell was going with his best lineup to win the game. Implicit in that lineup, however, is his doubt about starting Bradley, against even a righty starter.
A word more about sample sizes. Yes, they are small, but the Sox also look at how the player conducts himself in an at bat. Plus they get to watch him in batting practice, and they know what he has done at Pawtucket and Portland. So they actually know a lot more about him than just those bare statistices for 29 or 33 games, which is why, when they brought Pedroia up in 2007 to be the regular secondbaseman, they stayed with him despite the bad early spring.
One more piece of evidence is Iglesias-- last year when he played 25 games with an OPS of .391. Again, another small sample size, but all those other insights would apply to him. As a result, the Sox went after Drew despite having already committed $10M to Iglesias as a minor league player. That's a huge investment, suggesting he was the heir apparent to the SS position, but they were ready to walk away from it or at least take a couple of steps. Drew only has a one year contract. On the other hand, Bogaerts might just be a decent fielder and his OPS with three years less experience than Bradley or Ellsbury (in 2007), is a decent .779. This year Iglesias started out like a house afire at the plate, but hit a big slump in July. So, with Drew and Bogaerts as good options, it wasn't hard to give Iglesias up for a front line starter, Peavy.
The same thing could happen to Bradley if he can't hit. So far he is helping to make the case for keeping Ellsbury or making a deal for a good hitting outfielder. One other factoid helps Bradley, however, and that is the Sox ability to win without Ellsbury. So maybe they will still let Ellsbury go and give Bradley another shot next year with Vic, Nava, Carp, and Gomes holding the fort in the outfielder.