SAN FRANCISCO -- Behind every successful Giants ballclub is an astute in-season trade.

Whether it was the 1980s, when Al Rosen turned around the franchise's fortunes as San Francisco's general manager, or the last couple of decades, with Brian Sabean at the helm, the Giants' postseason appearances were inevitably galvanized by a Deadline deal or two that put the team over the top.

Timing is everything, of course, and it seemed that Rosen and Sabean always waited for the right interval to pass before settling upon a deal. Agree on a trade too soon, and you'll give up too much talent in return. Wait too long, and another team's likely to grab the player you wanted.

Top in-season deals

Rosen knew that when he obtained the highly coveted Rick Reuschel from Pittsburgh in 1987. Sabean struck in timely fashion to get Javier Lopez, Ramon Ramirez, Marco Scutaro and Hunter Pence, who contributed to one or both of the team's World Series titles.

Here's one reporter's look at the five best in-season trades in Giants history:

July 5, 1987: Giants receive 3B-OF Kevin Mitchell and LHPs Dave Dravecky and Craig Lefferts from the Padres for 3B Chris Brown, RHP Mark Grant and LHPs Keith Comstock and Mark Davis.

This deal helped both clubs, but it did more for the Giants, primarily because of Mitchell. He went from being a complementary player to a premier slugger, helping San Francisco win the National League West in 1987 and reach the World Series in 1989. He won the NL Most Valuable Player Award in the latter season, batting .291 with 47 homers, 125 RBIs and a 1.023 OPS.

Dravecky became a useful member of the starting rotation and a Giants legend when he overcame a cancerous tumor in his throwing arm to resume pitching. But his humerus bone snapped in his second comeback start, prompting his retirement. Lefferts was a competent reliever for San Francisco. The Padres didn't come up empty, as Davis won the NL Cy Young Award with 44 saves in 1989.

July 30, 2001: Giants receive RHP Jason Schmidt and 1B-OF John Vander Wal from the Pirates for OF Armando Rios and RHP Ryan Vogelsong.

Schmidt owned a sub-.500 career record (49-53) when he joined the Giants. He developed into one of the most successful pitchers in the franchise's San Francisco history, posting a 78-37 record for a .678 winning percentage that bested Hall of Famer Juan Marichal's .630 (238-140). Schmidt was a three-time All-Star as a Giant and set the club's single-game strikeout record with 16 on June 6, 2006, against the Marlins.

Neither Rios nor Vogelsong did much with the Pirates. However, Vogelsong thrived for the Giants after signing with them as a free agent in 2011. He made the All-Star team that year and was the club's leading winner (3-0) in the 2012 postseason.

Aug. 21, 1987: Giants receive RHP Rick Reuschel from the Pirates for RHPs Scott Medvin and Jeff Robinson.

If the Mitchell-Dravecky-Lefferts trade pointed the Giants in the right direction, this one propelled them forward. Reuschel quickly settled into the role of staff ace, winning five games down the stretch and following that with a 19-11 finish in 1988.

Reuschel had his last truly productive season in 1989, finishing 17-8 with a 2.94 ERA and winning the Game 5 clincher of the NLCS against the Cubs.

July 30, 1996: Giants receive LHP Kirk Rueter and RHP Tim Scott from the Expos for RHP Mark Leiter.

Rueter solidified the Giants' rotation for the better part of a decade (1996-2005). Durable and always willing to take the ball, he started 277 games, third on the all-time San Francisco-era list behind only the Hall of Fame combo of Marichal (446) and Gaylord Perry (283). Rueter also trails only Marichal (238) and Perry (134) with 105 wins in a Giants uniform.

July 27, 2012: Giants receive 2B Marco Scutaro from the Rockies for INF Charlie Culberson.

July 31, 2012: Giants receive RF Hunter Pence from Philadelphia for RF Nate Schierholtz, C Tommy Joseph and RHP Seth Rosin.

It's kind of difficult to mention one trade without the other. Together, these deals helped blaze San Francisco's path to its second World Series title in three years. In 61 games as a Giant, Scutaro hit .362 with 44 RBIs. He also batted .500 in the NLCS against St. Louis to win MVP honors. Pence, a leader on and off the field, drove in 45 runs in 59 games despite hitting only .219 as a Giant.