SAN FRANCISCO -- By their nature, baseball players are competitive people. They have to be in order to forget their disappointments, to remain confident in a sport where a 35-percent success rate is considered top-notch.

When playing against friends, people with whom they can boast about their achievements, the competition rises to another level. Ask Rajai Davis or Emmanuel Burriss, former Giants teammates who are now playing against one another in the Battle of the Bay.

The outfielders were friends in San Francisco before Davis was designated for assignment and immediately claimed by the Oakland A's. Davis was sad to leave a clubhouse where he was universally liked, but glad to find a spot on a team in the same area.

In the second game of a three-game series at AT&T Park, the former friends and current competitors will be trying to help their respective teams, and notch some bragging rights against one another.

"We're here first to win a ballgame and do what we have to do to help the team," Davis said. "But, yeah, you do want to turn it up a notch against the guys that you know."

In his first Major League season, Burriss is batting .282 in 35 games with six stolen bases. Playing against the A's for the first time, he'll try to help pitcher Matt Cain (3-4) even his pitching record. Cain won his last start (6 1/3 innings, one run against the Nationals), but has struggled recently, causing his ERA to balloon to 4.43. In four career starts against Oakland -- two in 2007 -- Cain is 1-3 with a 3.25 ERA in 27 2/3 innings.

Davis couldn't buy a hit in 12 games with the Giants this season, but has managed to hit .235 with seven stolen bases in 37 games with the A's. He remembers seeing Cain pitch in batting practice when he was with San Francisco, but he knows BP pitching and in-game pitching are two completely different things.

"What I saw was Spring Training stuff," Davis said. "Those guys don't throw the same pitches when the games start to really count."

So what would be a bigger thrill for Davis: getting a hit against his old teammates, or throwing out one of his buddies from the outfield?

Both, obviously. He enjoyed playing with the Giants, but now "it'll be nice trying to beat them," he said.

Not surprisingly, Burriss feels the same way. A win against a cross-bay, Interleague rival is his top priority, but nailing Davis at home plate would be pretty sweet, too.

"He's always talking about how fast he is," Burriss said. "I'll definitely rub it in his face if I get him. And if he throws me out, I'm sure I'd never hear the end of it."

Pitching matchup
SF: RHP Matt Cain (3-4, 4.43 ERA)
After struggling to find his command, Cain spent the week consulting with the team's other pitchers and coaches. His practice paid off on Monday as he displayed strong command in a 3-2 victory against Washington. After the game, he said he felt confident during the outing, and will look to keep his aggressive mentality against Oakland.

OAK: RHP Rich Harden (3-0, 2.85 ERA)
Harden got his third consecutive no-decision in his last start against the Angels, pitching six effective innings while surrendering three runs on six hits and three walks with a season-high-tying nine strikeouts. The highlight of his 99-pitch outing were the first nine pitches he threw in the game that struck out the side.

Tidbits
Before the Giants decide on a course of action for Merkin Valdez, the right-hander will undergo a nerve test on his injured throwing elbow this weekend and will visit Dr. Lewis Yocum for a second opinion next week. Although Yocum performed Tommy John elbow-ligament replacement surgery on Valdez in September 2006, Giants head athletic trainer Dave Groeschner re-emphasized that Valdez's current injury is unrelated to the surgery. ... Groeschner said "it's definitely possible" that infielder Kevin Frandsen's injured left Achilles tendon could heal quickly enough to allow him to play in a game at some professional level before the season ends. But Groeschner indicated that this is unlikely to happen if Frandsen endures any sort of setback. Frandsen, who has been cycling, walking and playing catch, is itching to begin hitting but won't start doing so until his range of motion improves. ... ESPNdeportes.com reported on Thursday that the Giants have agreed to sign Rafael Rodriguez, a 16-year-old Dominican outfielder, for what would be a team-record $2.5 million signing bonus. International players aren't allowed to officially sign before July 2. ... Maybe it was the Mohawk. Before stealing home in the second inning on Friday night, Omar Vizquel had his hair in a Mohawk in the clubhouse while dancing to salsa music.

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Up next
• Sunday: Giants (Kevin Correia, 1-3, 4.50) vs. Athletics (Dana Eveland, 4-5, 3.76), 1:05 p.m. PT
• Monday: Giants (Tim Lincecum, 8-1, 1.99) vs. Tigers (Justin Verlander, 3-9, 4.65), 7:15 p.m. PT
• Tuesday: Giants (Jonathan Sanchez, 6-3, 4.26) vs. Tigers (Kenny Rogers, 4-4, 4.74), 7:15 p.m. PT