This could be problematic. The Tampa Bay Rays have been without their best player for much of the 2012 season thanks to a severe hamstring issue, and it's kept them from ever performing as expected. They posted a 41-44 record without Evan Longoria, and while part of that was also due to missing players like Matt Joyce for stretches, Longoria's absence can't be understated in terms of its negative impact on the Rays.
The samples are small, but Tampa Bay's Dave Haller reports that the Rays scored 3.9 runs per game without Longoria in those 85 games, while they plated 4.6 per game with Longoria around in the season's first 23 contests. Tampa Bay is still in this thing thanks to their great start: they sit two games back of the wild card in spite of Longoria's extended absence, and two games up on Boston in the same race.
The Red Sox weren't able to take advantage of Longoria's absence thanks to injuries of their own, most recently that of David Ortiz, whose Achilles problem has sent Boston into a similar run-scoring spiral. While the Red Sox will once again have all of their best players back soon, between the returns of Ortiz and reliever Andrew Bailey, they only managed to keep things close with their AL East rival, rather than pass them for good, while their top player was on the shelf. That's a credit to Tampa Bay as much as it's a Boston failure, not that either club played especially well through the duration of his absence.
There are excuses on both sides for why that is, so don't consider this a blame session. It's just the facts of how things played out in a world without Longoria, where things should have been easier than they now will be.
Hat tip to the revived Process Report for pointing this out.