If not for an injury to Barry Zito in mid-April, Vogelsong might not be a part of the starting rotation.
Vogelsong looks to continue his dominance while Zito will make his first start in 2 1/2 months in Tuesday's day-night doubleheader against the Chicago Cubs at Wrigley Field.
Zito (0-1, 6.23 ERA), who will start the nightcap, opened this season as the No. 4 starter but only took the ball three times. He left his start against Arizona on April 16 with a right foot sprain and was put on the disabled list for the first time in his career.
Zito's trip to the DL opened the door for Vogelsong (5-1, 1.86), and the journeyman right-hander has taken full advantage of his opportunity.
Vogelsong has yielded two runs or fewer in 10 of 11 starts and has a major league-best 1.23 ERA since May 8. He allowed a run, four hits and a walk in seven innings of a 5-1 victory against Minnesota on Wednesday.
Vogelsong, who made his major league debut in 2000, played in Japan from 2007-09 and was in the minors last season, is now receiving strong consideration for a spot on the NL All-Star team.
"We have some time here, and I don't want to get ahead of ourselves," manager Bruce Bochy told the Giants' official website. "This guy's pitched great. That's how well he's thrown, to have his name mentioned."
The Cubs are fully aware of how well Vogelsong has pitched.
Vogelsong allowed seven hits and struck out seven in a rain-shortened, 3-0 complete-game win at Wrigley on May 14. The game was called in the seventh inning.
It also rained the following day, and the opener of the doubleheader is a makeup from that postponement.
San Francisco (44-34) arrives in Chicago riding a five-game winning streak after dropping a season-high five in a row.
The Giants capped a sweep of Cleveland with a 3-1 win Sunday, as Aubrey Huff drove in his team-leading 39th run. San Francisco, last in the majors with 265 runs, is 19-5 when Huff has an RBI.
The Cubs (32-46) are coming off a 7-3 win over Colorado on Monday, a makeup of an April 27 rainout.
Although the Cubs are struggling, Vogelsong and Zito will have to be careful pitching to Pena and Ramirez.
Pena leads Chicago with 16 homers and has gone deep seven times in the last 11 games. He is batting .316 with two home runs in 19 at-bats against Zito but hasn't faced the left-hander since 2006.
Ramirez has hit six of his eight homers in the last 19 games and is 8 for 16 in his last four.
"I'm more comfortable," Ramirez said. "I'm driving the ball more."
Ramirez is 5 for 12 with two homers against Vogelsong and 4 for 10 with a homer and double versus Zito.
Zito is 1-3 with a 4.84 ERA in six starts against Chicago.
Davis gave up four runs and eight hits in five innings in Wednesday's 4-3 loss to the Chicago White Sox, as the Cubs fell to 1-7 in the left-hander's starts.
Davis made his Cubs debut opposing Vogelsong last month, allowing three runs and four hits in five innings.
Lopez has worked primarily out of the bullpen for Chicago. In his lone start against Houston on May 30, the right-hander permitted six runs and 10 hits over 4 2-3 innings but did not receive a decision in a 12-7 loss.
He is 0-3 with a 6.97 ERA in six starts against the Giants.