By Morris Phillips

SAN FRANCISCO — Given the Colorado Rockies’ history of harvesting sluggers over the last 26 major league seasons, David Dahl’s accomplishment on Wednesday ranks as no small feat.

Dahl’s grand slam off Jeff Samardzija propelled the Rockies in a 6-3 series clinching win as the centerfielder became the first Colorado player to hit a slam in San Francisco.

Not Larry Walker, Todd Helton, Nolan Arenado or the Big Cat, Andres Galarraga, but Dahl, the Rockies’ emerging talent with just over 200 big league contests under his belt.

“Days like today validate what you’re seeing from David,” manager Bud Black said of Dahl. “I think it’s great. I know that his motivation and his desire is to be the best player he can be, and he’s working hard and what I like is he’s doing it on both sides.”

Dahl’s 10th home run of the season wiped out the Giants’ early 2-0 lead, and was largely responsible for pinning a loss on Samardzija, who surrendered five runs on just three hits in five innings. Samardzija followed Drew Pomeranz and Madison Bumgarner on the strikeout parade, fanning six, but he couldn’t get a big out facing Dahl when he needed it.

“A two-run homer and we’re fine there, and the game’s still going our way. But when it’s four it’s unfortunate,” Samardzija said.

The Giants struck for two runs in the first, interrupting a 13-inning scoreless streak, but after Pablo Sandoval’s solo shot off Rockies’ starter German Marquez in the third, the bats went quiet again. The Giants were shutout for the fifth time at home on Monday, and scored just five runs in the series. On Wednesday, when Marquez departed, things really dried up: the Giants managed just one base hit over the final four frames.

Marquez wasn’t particularly sharp, allowing seven hits, two runs and the home run to Sandoval, but he didn’t need to be with Dahl contributing five RBI to the cause, and allowing the Rockies to lead from the third inning on. Marquez picked up his second win this season at Oracle Park, having limited the Giants to one-hit on April 14.

“German was off. It was a combination of not his usual breaking balls and lack of fastball command,” said Black. “He had to work really hard to get through that.”

The Giants tinkered with their lineup–moving Brandon Belt into the leadoff spot, spelling the scuffling Evan Longoria with Sandoval, and giving Buster Posey a day off from his catching duties–but not much of that tinkering took hold after a rare, first inning outburst.

The Giants open a four-game set on Thursday against the Diamondbacks, who just bounced back from the losing a series to the Giants over the weekend by taking two of three from the first-place Dodgers.

Only the Marlins (30-48) have a worse record than the Giants among the 15 National League clubs. The Giants have been particularly deficient at home winning just 16 of their 39 contests so far.

Arizona’s Alex Young will face the Giants’ Tyler Beede in the series opener on Thursday.