Melillo was one of two players who were designated for assignment by the A's on May 30, when right-hander Kiko Calero was reinstated from the 60-day disabled list and righty Brad Ziegler was added to the 40-man roster.
Melillo, 26, batted .260 with five home runs and 17 RBIs in 38 games at Triple-A Sacramento. He was drafted by the A's in the fifth round of the 2004 First-Year Player Draft and made his Major League debut with Oakland last season. He appeared in one game on June 24 and walked as a pinch-hitter.
Fiorentino, 25, was designated for assignment when the A's reinstated third baseman Eric Chavez from the 60-day DL on May 29. He was on the A's Opening Day roster in Japan and had an RBI single in his only at-bat with Oakland before he was optioned to Sacramento on March 29, when rosters were reduced from 28 to 25.
He was hitting .273 with three RBIs in eight games with Sacramento in a season shortened by a stay on the River Cats DL from April 6 to May 20 with a broken nose. The A's originally claimed Fiorentino off waivers from Cincinnati on Jan. 25 after the Reds claimed him off waivers from Baltimore on Jan. 4.
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.