SAN FRANCISCO (Map, News) - Despite the dramatic debut of John Bowker, it will probably be two years minimum before enough prospects get to San Francisco to turn the Giants into a contender again.

It could be even longer than that for the most intriguing prospect, Angel Villalona, the Dominican teenager signed to a huge bonus last year, who has been compared to Albert Pujols, Miguel Cabrera and Frank Thomas.

“It could be four years,” new farm director Fred Stanley told me. “When he gets here, we want him to stay. We’d like to get him 400 games in the minors.”

The Giants had six choices in the first round of last year’s draft. It’s far too early to predict their future, but there are a couple who jump out.

» Tim Alderson: The Giants’ second selection (22nd overall) was 12-0 at Horizon High School of Scottsdale, Ariz., with an ERA of 1.05.

» Nick Noonan: A sandwich pick, he had a career average of .505 at Francis Parker High of San Diego. He played 52 games in the Arizona Fall League and hit .316.

On the major-league level, Bowker and shortstop Brian Bocock have the most potential because they’re relatively young, 24 and 23, respectively, so they have a chance to improve.

Bowker is the first Giants player to hit home runs in his first two games. Sometimes, a fast start presages greatness, as it did for Willie McCovey, who went 4-for-4 in his Giants debut, or Will Clark, who homered off Nolan Ryan in his first major-league at-bat. On the other hand, one of the eight Giants who homered in his first game is Johnnie LeMaster. Enough said.

Bowker has a nice swing and legitimate power. He hit 22 home runs, a franchise record, at Double-A Norwich, which has a huge park, and his home run on Sunday landed high in the seats in the arcade.

Bocock, in the majors only because Omar Vizquel is recovering from surgery, is clearly overmatched by big-league pitching. But he is extraordinary in the field. If he can go back to the minors, work on his bunting and learn to slap the ball around, he could maybe hit .250 for the Giants, which would be enough because of his glove.

Meanwhile, on the major-league level, the Giants need to be ruthless in evaluating their over-30 veterans.

Even when he returns from surgery, Dave Roberts should sit so Fred Lewis can play. So should Ray Durham — then the Giants can find out if Eugenio Velez can be a competent second baseman (Stanley thinks he might be better in the outfield). Because Daniel Ortmeier is hitting only from the right side now, the Giants want him to have extended batting practice against right-handed pitching before they use him against right-handers, so Rich Aurilia is playing. But when Ortmeier gets into the starting lineup, he should stay. I’d even trade Randy Winn, just to give Bowker, Lewis and even Rajai Davis adequate playing time to prove themselves.

Are any of these players good enough? I don’t know, but the only way to find out is to play them. The Giants won’t contend with the over-30s anyway.

I believe the fans would be patient with this approach. I walked around the park at the home opener and talked to many, many fans who wanted to see the younger players.

So, it’s up to the Giants now.

Glenn Dickey has been covering Bay Area sports since 1963 and also writes on www.GlennDickey.com. E-mail him at glenndickey@hotmail.com.