Henry refused to go over the cap and pay the tax penalty caused by Sandoval's $19M salary, depriving the Champion Red Sox of a top closer. It turns out that has been the difference all season, if you count the 20+ blown saves. The team just didn't have a closer commensurate with the abilities of the rest of the team. It lacked a bullpen anchor, and it still doesn't have one. They've scored 10+ runs each in the first three games against NY, and they needed them.
The other factor was the overmanaging of Sale--with good intentions, but it just didn't work out. He just couldn't get his rhythm. Is there a harder word to spell than rhythm? I have to look it up every time.