According to recent research done by Ben Lindbergh over at Grantland, the Mets have the second-longest extant transaction tree in baseball. In short, the idea of this research was to look at how each player was acquired by each team and trace back moves that led them to this acquisition.
For example, David Wright, the longest-tenured player on the Mets by a wide margin, can be traced back to Mike Hampton signing with the Rockies after the 2000 season, giving the Mets the compensatory pick used to select Wright in the 2001 draft. However, Wright's tree doesn't stop there.
The Mets signed pitcher Terry Leach as a free agent on July 27, 1980. In September of 1983, he was traded to the Cubs for Mitch Cook and Jim Adamczak. Nearly a year later, the Mets packaged Cook, Manuel Lee, and Gerald Young in a trade with the Houston Astros for third baseman Ray Knight.
After Knight's World Series MVP performance in 1986, he was let go by the Mets and signed with the Baltimore Orioles instead. This gave the Mets a second-round compensation pick, which they used to draft catcher Todd Hundley in 1987. In December of 1998, over ten years later, the Mets traded Hundley and minor leaguer Arnold Gooch to the Dodgers for Charles Johnson and Roger Cedeno.
Then, on December 23, 1999, the Mets traded Cedeno, Kyle Kessel, and Octavio Dotel to the Astros for Derek Bell and the main link to this whole tree, Mike Hampton.
Here's a visual representation of all these transactions from the article:
Mike Hampton would go on to win 2000 NLCS MVP for the Mets and, most importantly, give the team the draft pick that would become one of the best players in franchise history. It's safe to say that trade with the Astros worked out just fine.
When general manager Frank Cashen signed Terry Leach in 1980, chances are he had no idea that he'd start a string of transactions that would lead to the drafting of a future captain of the franchise.