Bailey is in his last year of arbitration after this season. He isn't ready until next August after his surgery. I bet he is non-tendered and re-sign a minor contract, saving a roster spot for other player(s).
Cherrington including a vesting option for Uehara is genius. He will make the same next season at 4.2M. Had Uehara went to arbitration instead, he would get 7M with the season he is having. This saves them about $3M to target other relievers. Plus they are off the hook with $15M invested in Hanarahan, Bailey and Aceves in 2013.
Also I can't believe anyone want Tazawa gone. Since 2012, he has pitch 90 games, 98 inning for Boston with a 2.00ERA