After spending much time at baseball-reference.com and retrosheet.com, I've found that since 1969, only one pitcher traded at the July trade deadline has won a World Series game for his team. That pitcher was Jim Clancy, who was traded on July 31, 1991 by the Houston Astros to the Atlanta Braves for Matt Turner and a player to be named later (minor leaguer Earl Sanders was later sent to the Astros to complete the trade).

 

Clancy pitched the last 1/3 of the 12th inning in game 3 of the 1991 classic between the Braves and Twins. Clancy relieved Kent Mercker who had just struck out Kent Hrbek. Dan Gladden was on third and Chuck Knoblauch had just stolen second. Clancy intentionally walked Kirby Puckett to load the bases for pitcher Rick Aguilera who lined out to center to end the inning.

 

In the bottom of the inning, Mark Lemke lined a single to left field off of Aguilera to score David Justice and win the ballgame for Atlanta, and thus making Jim Clancy the first and only pitcher since 1969 traded at the July trade deadline to win a World Series game.

 

 

Graeme Lloyd won game 4 in 1996 for the Yankees against the Braves. Lloyd was traded after the non-waiver deadline in 1996 from the Brewers to the Yankees making him the only pitcher traded after the non-waiver deadline to win a World Series game since 1969.

Sorry you did all that research on a topic that was discussed all last July.

 

Pitcher wins or playoff success is such a poor measurement. Most teams add pieces in July just to reach the playoffs. Very rarely do you find a top player that would jump to the head of a playoff rotation. More often a good #3 starter is available.