In this Baseball Daily Digest piece, they break down what happened with Michael Bourn from 2008 to 2009:
He saw a heater 65.1 percent of the time, one of the 20 highest rates among all hitters. Bourn was helpless when pitchers challenged him. Per 100 pitches seen, he had a -1.18 run value against fastballs, fourth-worst in the majors. He also struggled with breaking balls (-0.56 per 100 pitches vs. sliders, -0.41 vs. curveballs) and changeups (-4.03).
Bourn wasn’t blown away by fastballs this time around. Against the heat, he had a +1.35 run value per 100 pitches in 2009. One year after ranking as one of the most feeble fastball hitters in the majors, Bourn showed marked improvement. His percentage of fastballs seen dipped from 65.1 to 60. Bourn still struggled against secondary stuff (-2.23 runs/100 against sliders, -0.44 vs. curveballs, -1.29 vs. changeups), however.
His strike zone judgment showed modest improvement. Bourn swung at 20.3 percent of pitches off the plate, while increasing his in-zone swing percentage to 60.6. With fewer fastballs seen, Bourn’s percentage of pitches within the zone dropped to 49.3. That helps explain the increase in free passes taken.
So what about 2010?
Going forward, Bourn will likely see some regression in his performance. Sean Smith’s CHONE projects the 28 year-old to hit .268/.338/.368, with a 99 wRC+. That would make Bourn about 1 run below average per 600 plate appearances. Jeff Zimmerman’s projected 2010 UZR totals peg Houston’s center fielder as a +4 defender per 150 defensive games. You can also credit him with a few extra runs for his base advancement prowess. Those totals mean Bourn projects as a two-and-a-half to three win contributor in 2010. That’s still a pretty nice piece to have.
I have no mathematical basis to back this up, but I don't think Bourn will regress as much as the CHONE projections think (but they're a lot more accurate than I am). But I do appreciate the note about his defensive prowess and his ability to advance, thanks to his ability to run from first base to second base before the pitcher has an opportunity to deliver the ball from the pitcher's mound to home plate and the catcher then relay the ball to the second baseman.