On December 4, 2008, Rentería signed a two-year, 18.5 million dollar deal with the San Francisco Giants with an option for 2011.
He had five RBIs and became the first player to hit a grand slam off Jake Peavy in an 8–3 victory over San Diego on April 21, 2009.
On April 29, he had four hits in a 9–4 victory over the Dodgers.
He tied an eventual 7–4 loss to the Mets on May 14 with a single in the eighth inning, but he strained a hamstring advancing to first base and had to leave the game with an injury.
He missed six games with the injury before he returned to the lineup on May 22.
From May 8 through June 6, despite batting only .250, he reached base safely in twenty straight games.
He had a game-winning grand slam on August 30, which gave the Giants a 9–5 win over Colorado.
He missed nineteen of the final twenty games of the season with biceps tendonitis and a sprained AC joint, and on September 26 he had surgery to remove bone spurs and chips from his right elbow.
Dealing with injuries all year, Rentería finished the season with a career-low .250 batting average and only 115 hits and 48 RBI.
On December 4, 2008, Rentería signed a two-year, 18.5 million dollar deal with the San Francisco Giants with an option for 2011. He had five RBIs and became the first player to hit a grand slam off Jake Peavy in an 8–3 victory over San Diego on April 21, 2009. On April 29, he had four hits in a 9–4 victory over the Dodgers. He tied an eventual 7–4 loss to the Mets on May 14 with a single in the eighth inning, but he strained a hamstring advancing to first base and had to leave the game with an injury. He missed six games with the injury before he returned to the lineup on May 22. From May 8 through June 6, despite batting only .250, he reached base safely in twenty straight games. He had a game-winning grand slam on August 30, which gave the Giants a 9–5 win over Colorado. He missed nineteen of the final twenty games of the season with biceps tendonitis and a sprained AC joint, and on September 26 he had surgery to remove bone spurs and chips from his right elbow. Dealing with injuries all year, Rentería finished the season with a career-low .250 batting average and only 115 hits and 48 RBI.
Édgar Rentería