DeLeon had a record of 3-22 in the season and a half before Bucs GM Syd Thrift somehow was able to exchange him for a future six-time All-Star at two different positions (outfield and third base) and a cornerstone of the Pirates' glory run in the early 1990s.
No. 2: May 17, 1956 -- Pirates receive Bill Virdon from the Cardinals for Dick Littlefield and Bobby Del Greco.
In exchange for a career utility man and a journeyman pitcher, the Bucs acquired an elite defensive center fielder for a decade, and a centerpiece of their 1960 World Series championship club. The bespectacled Virdon, who later even managed the Pirates, among other teams, had a knack for blanketing Forbes Field's vast center field and was the ideal leadoff hitter in Danny Murtaugh's lineups.
No. 3: Aug. 26, 2003 -- Pirates receive Jason Bay, Oliver Perez and Corey Stewart from the Padres for Brian Giles.
The Pirates spent much of Giles' fifth and final very productive season with Pittsburgh looking for the best return they could get to move the high-priced outfielder, and when they finally pulled the trigger, the Bucs hit a bull's-eye. Bay became the first National League Rookie of the Year Award winner in franchise history. While Perez's shelf life was brief, he did have a monster 2004 season, with a 2.98 ERA in 30 starts and 239 strikeouts in fewer than 200 innings.
No. 4: April 1, 1987 -- Pirates receive Andy Van Slyke, Mike LaValliere and Mike Dunne from the Cardinals for Tony Pena.
True, Pena was a four-time All-Star when this eve-of-the-season deal went down, but it still ranked as an immediate steal for the Bucs. Pena batted .214 that season while LaValliere more than ably replaced him behind the plate and Van Slyke began collecting Gold Gloves and All-Star honors.
No. 5: June 3, 2009 -- Pirates receive Jeff Locke, Charlie Morton and Gorkys Hernandez from the Braves for Nate McLouth.
This is the perfect example why trades take years for honest evaluation. Locke has become the young lefty ace of "the next good Pirates team," while Morton, at 29, still can make a strong comeback from Tommy John surgery. Although McLouth is having a nice career resurgence in Baltimore, he really is not missed in the Bucs' new outfield. Don't forget -- he was moved to clear center field for Andrew McCutchen.