Fontenot won't have to travel far to join his new team. The Cubs are currently in the midst of a series in San Francisco. Fontenot burned the Giants with a two-run pinch-hit double during the Cubs' win Tuesday.
"It's strange to be traded in the same city you're in," Fontenot said. "I'm excited about the opportunity [with the Giants]. I've had a great time [in Chicago].
"[The season] has been tough. But as far as my performance, I'm pretty happy with it. I've always been a team guy. Things haven't gone the way we wanted them to."
The 30-year-old Fontenot, originally a first-round pick of the Baltimore Orioles, spent all four of his big league seasons with the Cubs.
The Giants were in negotiations with the Cubs to acquire Fontenot at the July 31 trade deadline. Talks picked up between Cubs general manager Jim Hendry and Giants GM Brian Sabean after San Francisco shortstop Edgar Renteria strained his left biceps and went on the disabled list Wednesday, Renteria's third stint on the DL this season.
"These discussions had begun before the trading deadline," Bush said. "Jim and Brian Sabean are at the owners' meeting and they finished it off today."
Renteria underwent an MRI exam earlier Wednesday for the injury that began bothering him on a swing during last week's series at Atlanta.
"Mike will help us in the infield, give us experience and a left-handed bat," Giants manager Bruce Bochy said. "I wish we had him a day earlier."
The 30-year-old Fontenot was traded to the Cubs for Sammy Sosa in 2005. He is batting .284 with one home run, 11 doubles, three triples and 20 RBIs in 75 games this season. Of his 40 starts, 29 have been at second base, seven at third and four at shortstop.
He could spell Freddy Sanchez at second while also filling in at other positions.
The Giants also activated infielder Eugenio Velez from the disabled list and optioned him to Triple-A Fresno. Velez was struck on the head July 25 by a foul ball while in the dugout against Arizona.
The Cubs will call up Darwin Barney from Triple-A Iowa to take Fontenot's place. The team is hoping he will be on the field for Thursday's game in San Francisco.
Crawford is a 22-year-old center fielder playing for Class A Augusta. He's hitting .255 with four homers, 29 RBIs and 24 stolen bases, but he has struck out 108 times against only 35 walks.
Bruce Levine covers the Cubs for ESPNChicago.com. Information from The Associated Press was used in this report.