In a nutshell: By this point in the game, Valdez was the only player left for manager Charlie Manuel, who knew how to get the ball over the plate, other than his starters. Manuel didn't want to risk using one of his starters so he pulled Valdez from the infield and handed him the ball. Valdez went on to pitch a scoreless top of the 19th and eventually got the win when the Phillies scored in the bottom of the 19th. For the record, Valdez retired Joey Votto, hit Scott Rolen with a pitch and then went on to retire Jay Bruce and reliever Carlos Fisher .
Valdez is the first position player to earn a major league pitching win since catcher Brent Mayne of the Colorado Rockies did it on August 22, 2000.
When Mayne got his win he wasn't already in the game so I guess we can say he was brought in as a pinch-pitcher. According to the Elias Sports Bureau, Valdez, who was already playing a position in the game, became the first player since Babe Ruth to earn a win as a pitcher after having started the game at another position. Ruth did it on October 1, 1921 at the Polo Grounds, starting the second game of a doubleheader against the Philadelphia Athletics in left field, and then pitching the final four innings of that 11-inning game. Ruth allowed six runs, but got the victory when New York scored in the bottom of the 11th inning to win, 7-6.
So anytime a player does something that was last done by the Sultan of Swat it definitely deserves a mention. Wilson Valdez meet The Bambino.