Courtesy of Deadspin comes this peculiar picture of Jake Peavy during yesterday's game, notice his throwing hand.
Obviously there's SOMETHING on his fingers, the questions are what is it? Dirt? Pine tar? Grease from his car? Does he use it often? Does it help him with movement? Peavy is one of the better pitchers in the game so this is a bit disappointing if he's been doctoring balls -- although not completely unexpected. Players will naturally try to and gain an advantage through unnatural ways by using whatever means they can come across.
I always refer to Derek Zumsteg's Cheater's Guide to Baseball book and blog in these situations. Zumsteg's book is a must buy, and on the book's blog he's covered and broken a ton of "cheating" in the big leagues. Remember the Francisco Rodriguez and Manny Corpas scandals? Those were Zumsteg's findings.
As Dex over at Gaslamp Ball brings up, Peavy is a chewer, so it's possible that's just residue from his nasty habit. Dex also points out how impressive it would be if Peavy were spitballing and didn't get caught. The second base umpire would've had to see that, right? Or a hitter, runner, coach, someone had to see his hand.