Here's how I see Bard's career progression:
2004-2006 (NCAA) - He didn't have great control, and threw mostly fastballs, but his stuff was good enough that he could get away with it against this level of competition.
2007 (A/A+) - The Sox toyed with his mechanics after drafting him, and the results were disastrous. His already iffy control got much worse, his stuff became pedestrian, and suddenly batters had no reason to swing early in counts. He'd fall behind and have to groove fastballs in the low 90s, and hitters were taking their walks or jumping on the grooved fastballs. Here's a quote from Bard himself:
I was at 90 to 93 with a crappy curveball and a changeup I couldn't locate. There were times I went out there and felt like I was pitching with someone else's mechanics and someone else's repertoire.
2008 (A/AA) - He was converted to relief, but more importantly, allowed to go back to his old mechanics. His control got better, back to where it was in college. The strikeouts, however, starting coming by the truckload. It is typical for pitcher's K rate to increase in relief, and Bard was also feeling comfortable again, and getting better, which is also typical for a pitcher in their early 20s.
2009-2011 (MLB) - We all know this story. Dominant reliever from the start, but a guy who's learned how to pitch over the last few seasons. The control has been better each year, the groundball rate has been better each year. His slider has developed into a nasty pitch, and has started throwing the changeup to lefties as another weapon.
Bard has been good to great at every level, and in every role, except for 2007. He wasn't a bad starter in 2007, he was just a terrible pitcher, period. He was throwing in the low 90s and couldn't hit the side of a barn. Is there any surprise that he sucked? Can we please stop talking about 2007 as being any sort of evidence about how Bard will perform as a starter in 2012? He's a guy that has always had good stuff, but needed to hone his craft and learn to pitch. We saw a similar development with Jon Lester at similar ages, even if he never got converted to relief.