The Rockies and San Diego Padres
Excluding purchases of players, the Rockies and Padres have only had four deals together and two of them were in the Rockies first season as a franchise. For the biggest deal, it is one of those two trades.
July 26, 1993–The Colorado Rockies traded a player to be named later, Brad Ausmus and Doug Bochtler to the San Diego Padres for Greg Harris and Bruce Hurst. The Colorado Rockies sent Andy Ashby (July 27, 1993) to the San Diego Padres to complete the trade.
Brad Ausmus was selected by the Rockies in the expansion draft in 1992 from the New York Yankees but before he reached the major leagues, the Rockies made this deal with the fledgling Padres. He made his debut with the Padres later in 1993 and played for the Padres, posting a 3.7 WAR until he was traded in the middle of 1996 with two others to the Detroit Tigers in exchange for catcher John Flaherty and infielder Chris Gomez.
He ended up becoming an All-Star and a 3-time Gold Glove Award winner in his 18 year career. He hung up the spikes after the 2010 season but he became the manager of the Tigers in 2014 and after one-year hiatus from managing, he is in his inaugural season as the manager of the Los Angeles Angels.
Bochtler, then a minor leaguer, made his MLB debut with the Padres in 1995 before being traded before the 1998 season. In three seasons with the Padres, he pitched to a 3.78 ERA (106 ERA+) in 151 games. He played his last major league game in 2000. Currently, he is the Padres bullpen coach.