I just wanted to pass on what I came across while reading up on some of the post-2008 minor league awards.
Going into 2008, Mad-Bum didn't have much of a breaking ball, and relied heavily on his fastball to get batters out. However, according to an interview with mlb.com posted on November 25th, Bumgarner said:
Q: Can you break down what he throws and what he’s working on?
A: He’s worked on a slider. He had a curveball in the spring but it was erratic. It seemed more like a knuckle curve to me and he wasn’t consistent with it. The slider has gotten better. He’s around the plate with it. It’s got a sharper break and more tilt.
But the biggest thing is the changeup. He’ll need that for the higher levels and he understands that. Down here, he’s just throwing the ball by guys. The closer to home plate they get, the more he reaches back and goes after them. For 19, he’s a very mature, smart kid. He knows he’s got some things he’s got to work on to make himself a more complete pitcher, not just a thrower.
Though none of the above information is definite, there are very good indications that Mad-Bum is developing very quickly and could be developing his secondary pitches much more quickly than anyone expected. If that's the case, the Giants could have a very talented young major league ready pitcher on their hands within the next 2 to 3 years.