The 38-year-old became the oldest player in franchise history to hit his first home run.
"I was just looking for a ball to hit the other way with a guy on second," Vogelsong said. "I just put a good swing on it. I didn't know [if it had a chance]. I know I hit it good, but when you don't have one, you don't ever know, I guess."
He didn't fare as well from the mound, however, exiting in the fourth inning with the Giants trailing, 7-2, after yielding two runs on three hits without retiring a batter. In all, he allowed eight runs (seven earned) on 11 hits while striking out one in three innings, raising his Coors Field ERA to 8.44 in seven starts.
His struggles took the luster off his milestone hit.
"I'm not enjoying it at all," he said.
"He was just a little flat," manager Bruce Bochy said. "He was missing his spots. The first inning, he had trouble making his pitches. Then he regrouped. Looked like he was getting in a groove there. He was off tonight, pretty simple."
Vogelsong's self-assessment was even more to the point.
"I just stunk," he said. "I didn't command the heater. Breaking ball was up. I couldn't throw well at all."
The Rockies batted around in the first inning, and by the time Vogelsong left the game, eight of the nine Rockies starters had at least one hit off him, matching his career high of 11 hits allowed.
"They've got a good lineup," he said. "They always have. And they swing the bats well. I know that their record doesn't show it, but they're a good, offensive team, and you have to make your pitches against them just like everybody else. If you don't, they're going to hurt you."
Vogelsong pitched a scoreless second and allowed an unearned run in the third before the Rockies chased him in the fourth.
"I felt like I was settling in a little bit, and then the wheels kind of fell off again," he said.