Giants manager Bruce Bochy had stated that Melancon, who was sidelined with a mild right pronator strain, likely would be activated before Friday's series opener at St. Louis.
Two factors hastened Melancon's comeback: The ever-growing confidence in his health, which was strengthened by his 22-pitch bullpen session on Monday, and the immediate need for late-inning relief help. Derek Law, who inherited the closer's duties from Melancon, pitched on four of the previous five days entering Wednesday.
Melancon, who hasn't pitched since May 3, owns a 2.53 ERA with six saves in eight opportunities over 11 appearances. The 32-year-old signed a four-year, $62 million deal with San Francisco this past offseason as a free agent.
Tomlinson, who has spent fractions of three consecutive seasons with the Giants, hit .240 (6-for-25) with one RBI in 15 games during this stint with San Francisco.