SAN FRANCISCO -- Yovani Gallardo instinctively hacked at the high fastball, not thinking much about the pitching great who had thrown it, and his three-run homer dropped sharply beyond the fence in the left-field corner.
Although Gallardo has been alive only slightly longer than Randy Johnson has been a major league pitcher, the Milwaukee Brewers' promising right-hander started off his season with an achievement even more remarkable than his solid effort on the mound.
He's the first pitcher ever to homer off the Big Unit.
Gallardo pitched neatly into the seventh inning while spoiling Johnson's debut with the San Francisco Giants, leading the Brewers to a 4-2 victory Wednesday night.
Gallardo (1-0) insists he'll remember his first victory in nearly 19 months much longer than the historic hit that made it possible. The 23-year-old gave up six hits and struck out six while muzzling a Giants team that scored 10 runs on opening day.
He was thrilled to see his impressive spring reflected in his first real game since early last season, when the second of two serious knee injuries in 2008 sidelined him for the rest of Milwaukee's playoff-bound campaign.
"There were a lot of things going into it, with my first start of the year after I wasn't able to start off with the team last year," Gallardo said. "There was a little bit of anxiousness there. The win, that's obviously the most important for me."
Everybody else will remember the homer. He smacked a two-out, two-strike pitch over the fence in the fifth, providing himself with all the run support he needed.
"Growing up and watching him pitch, he's a great pitcher," Gallardo said of Johnson, the 45-year-old right-hander. "Not very many people get the opportunity to do that. Rounding the bases, I was pretty excited."
After Bill Hall doubled with two outs in the fifth, Johnson walked Jason Kendall to face Gallardo. Although the Brewers understood the move, the dugout pulsed with excitement about Gallardo, known around the spring training cages as an above-average hitter.
"Nobody said anything, but we all kind of knew," said Milwaukee reliever Carlos Villanueva, Gallardo's close friend. "It's not as easy to get him out as you might think. ... That was a bomb. It's not surprising from him. You expect him to hit, but not an absolute bomb."
Although the Brewers lost top starters CC Sabathia and Ben Sheets following last fall's run to their first playoff berth in a quarter-century, Milwaukee might not miss them as much as many expect if Gallardo keeps living up to the considerable promise he showed in 2007 and again this spring.
Gallardo overshadowed the formal Bay Area homecoming for Johnson (0-1), who opened his 22nd major league season with seven strikeouts -- giving him 4,796 in his career -- in five often-dominant innings. Johnson allowed just four hits, but two were homers by Mike Cameron and Gallardo.
"I felt bad, because that took the sail out of the fans, I think," said Johnson, who got raucous ovations before the game and after most of his innings. "(Gallardo) pitched a good ballgame and got the big hit, too. That one at-bat, it gets lost how good I felt. But it's all a wash. I can't go out and pitch any better."
Randy Winn stole two bases for San Francisco and hit an RBI single in the seventh when Gallardo tired with two outs, leaving with two runners on base. Reliever Todd Coffey got Bengie Molina to dribble a harmless grounder with the bases loaded.
Villanueva pitched the ninth for his first save, filling in while presumptive closer Trevor Hoffman starts the season on the disabled list.
Johnson, who grew up in the East Bay suburb of Livermore, Calif., admittedly signed with the Giants to chase the final five wins necessary to join the 300-victory club, but also to provide veteran leadership to San Francisco's staff.
In his first inning with San Francisco, Johnson came within one pitch of striking out the side. He fanned Rickie Weeks and Corey Hart -- with a changeup -- and had two strikes on Ryan Braun before a harmless fly to center.
He retired Milwaukee's first five hitters, also striking out Prince Fielder, but Cameron then homered to left. Cameron entered the game 2-for-29 with 18 strikeouts in his career against Johnson.
"He threw great, (but) one pitch was the difference in the game," Giants manager Bruce Bochy said. "He had good stuff. It was just one pitch that he didn't get away with. That kid can swing a bat. We know it."
Before the game, the Giants formally presented the 2008 NL Cy Young award to Tim Lincecum. Mike McCormick, the only other San Francisco Giants pitcher to win the award, spoke to the crowd before Lincecum made a brief speech.
"Lastly and always, I just want to thank my dad," said Lincecum, who only made it through a career-low three innings while getting no decision in Tuesday's opener.
Johnson is the oldest pitcher to start a game for the Giants, surpassing Warren Spahn, who was 44 in 1965. He's their oldest player since 49-year-old Arlie Latham played four games for the New York Giants in 1909. ... Recently released Giants OF Dave Roberts was in the park in his new role as a member of the media, working on broadcasts in the Bay Area and San Diego. ... Gallardo made his major league debut against the Giants on June 18, 2007. He hit his first two career homers in August 2007 near the close of his solid rookie season.