"It frees things up to do what we want with Chad," manager Bruce Bochy said.
Ramirez, 31, was 2-1 with a 3.46 ERA in 20 games for Fresno. He had 31 strikeouts and 13 walks in 26 innings. A contender for a spot on the Opening Day roster in Spring Training, Ramirez was released and had to accept a role in the Minors after recording an 11.25 ERA in eight Cactus League appearances.
"In Spring Training, he was trying to get back in shape," Bochy said. "He has gotten better and better in Fresno."
From 2010-11, Ramirez was 4-3 with a 2.07 ERA in 91 appearances with the Giants before they traded him with outfielder Andres Torres to the New York Mets for outfielder Angel Pagan during the 2001 Winter Meetings. Ramirez re-signed with the Giants shortly before Spring Training, accepting a Minor League contract.
Ramirez excelled down the stretch in 2010 to help San Francisco reach the postseason. He posted a 0.67 ERA in 25 appearances after being acquired from Boston at the Trade Deadline.
To clear room for Ramirez on the 40-man roster, infielder Tony Abreu was transferred from the 15-day to the 60-day disabled list. Abreu remains on an injury rehabilitation assignment with Fresno.
Chris Haft is a reporter and Andrew Owens is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.