SAN FRANCISCO (AP) - Mike Fontenot has suddenly become a powerful presence in the Chicago Cubs ' lineup.

Fontenot homered for the third time in eight games, including a tiebreaking shot in the eighth inning to lift the Cubs to a 6-5 win over the San Francisco Giants on Wednesday night.

''I've been feeling good at the plate,'' said the second baseman, who had seven homers in 354 at-bats entering the game. ''I'm just trying to have good swings at the plate and I've been fortunate enough to hit some balls out.''

Jim Edmonds also homered for the Cubs, who have scored 16 runs in the first three games of this four-game series after being held to nine runs while getting swept by the Chicago White Sox over the weekend.

Carlos Marmol (2-3) picked up the win for Chicago despite giving up a tying three-run homer to Ray Durham in the seventh. Bob Howry pitched a perfect eighth and Kerry Wood worked the ninth for his 21st save.

Wood retired the first two he faced before Jose Castillo 's pinch-hit triple put the tying run on. The closer then got Fred Lewis to strike out looking to end the game.

''It turned into an exciting game, it really did,'' Cubs manager Lou Piniella said. ''There were a lot of big hits for both sides, with the biggest being Fontenot's as it turned out.''

Edmonds, who walked and scored in the second, hit a two-run homer off Giants starter Kevin Correia in the sixth inning to help lift the struggling Cubs to only their sixth win in 15 games.

Geovany Soto , attempting to become the first rookie catcher to start for the National League in the All-Star game, added a two-run single in the seventh and finished 2-for-4. Before voting ended Wednesday night, Soto was the runaway leader at his position with 650,000 more votes than runner-up Brian McCann of Atlanta.

A series win over San Francisco would be encouraging for the Cubs, who are slowly starting to return to full strength after being beset by injuries earlier in the year. Outfielder Reed Johnson (back spasms) is set to come off the disabled list Thursday, while ace Carlos Zambrano (right shoulder strain) is due to be activated in time to start Friday's game in St. Louis.

''It's always good to have those guys coming back, to have everybody healthy and ready to go,'' Soto said. ''But most important, it's the other guys, when those guys aren't around, stepping and getting the job done. It was good to see a guy like Fontenot hit a home run in that situation. It feels like guys are coming around.''

In addition to Johnson and Zambrano, Piniella said before the game that he expects cleanup hitter Aramis Ramirez back in the lineup for the finale against the Giants. Ramirez missed three games while attending the birth of his son in the Dominican Republic.

''We were to the point today where we couldn't even double-switch,'' Piniella said. ''We had to just stay steady and constant with our pitchers. At least tomorrow if Ramirez is here and with Johnson, all of a sudden now we can do a few things.''

Chicago starter Ryan Dempster pitched six strong innings but was denied his first road win in more than two years after Marmol gave up Durham's three-run homer in the seventh.

A closer for the Cubs last season, the right-hander gave up two runs on five hits while striking out seven. His only mistake came in the sixth when he gave up a two-run homer to John Bowker . It was Bowker's ninth home run of the season, a massive shot over the left-field wall that landed in McCovey Cove.

The Giants, who beat the Cubs 2-1 a night earlier, had eight hits but failed in their bid to win consecutive home games for the first time since June 1-2.

''It was a good comeback on our part. We just couldn't hold it,'' San Francisco manager Bruce Bochy said. ''We battled back off a tough pitcher. It was a good ballgame, we just made a mistake there in the eighth.''

Notes: The game was broadcast around the world to 176 countries and more than 200 U.S. Navy ships as part of ''Salute to the Military Night'' by the Giants and Comcast SportsNet Bay Area. ... The Giants signed 16-year-old pitcher Luis Angel Mateo from the Dominican Republic. The 6-foot-3, 175-pound right-hander is expected to begin playing in the Instructional League this fall. ... San Francisco C Eliezer Alfonzo , called up from Triple-A Fresno a day earlier, made a wild throw into center field while trying to catch Ryan Theriot stealing second base. Alfonzo started in place of Bengie Molina , who was given the night off. ... Slumping Giants SS Omar Vizquel went hitless in three at-bats and is batting .043 (2-for-46) over his last 15 games.