Tazawa has time to develop. Barring several injuries to the Rotation.
Bowden concerns all of us to some extent. I can't find the link, but there was an article on him in the Globe, Herald, or on ESPN Boston where he explained what happened to him last year. If I recall correctly, he said he was not prepared for relief work. He said he'd get up in the 2nd or 3rd to warm-up and then was not ready to go when called to duty innings later. Also, he said that the Sox are working with him on his mechanics. In any case this may be his last shot here. Even though he's still really young. I see him being traded at the deadline. Unless he dominates in Pawtucket.
I suspect YAB has hit it on the head. AAAA and gone.