Posted by Zach Sanders on Wednesday, September 9, 2009 at 1:00 am

Giants prospect Madison Bumgarner made his MLB debut last night against the San Diego Padres. Tim Lincecum was scheduled to make the start instead, but was scratched late due to back soreness. Before going to the Pitch F/x on Bumgarner, let’s read the scouting report from MLB.com:

“The left-hander debuted in pro ball with one pitch — though that offering was a plus, plus fastball that easily hits the mid-90s with good late life. His curve and slider have shown great progress and the changeup is improving as well, though perhaps lags a bit behind the others. He also has excellent command on both sides of the plate.”

Now, let’s see what the f/x has to say about it:

His velocity was down, way too far down. BP writer and scout Kevin Goldstein told his followers on twitter that “If you’re not worried about Madison Bumgarner’s velo drop over the last few weeks . . . you should be”, and added that his velocity “Was 93-94, touching 96 in late May. June was inconsistent, July consistently down”. This could be due to his innings pitched, but he pitched more innings last season than he has this year, so I doubt that. Maybe there is an underlying injury, but we really don’t know.

Other than that, his fastball actually has great cutting action, so much so that I could have called it a cutter if I wanted. His changeup, which he only threw twice, has good movement. His slider is OK, but it’d be better if it had more vertical break to it.

His armslot is what will really throw the hitter off, as it is almost of the page. The sidearm motion will make the slider and cutting fastball look even deadlier to a hitter, and even nastier to a lefty. If he doesn’t get his velocity back, he’s at worst a lefty setup guy who will dominate left handed hitters throughout the league.