A week after being released by Boston, Penny (1-0, 0.00 ERA) scattered five hits over eight innings in San Francisco's 4-0 victory at Philadelphia on Wednesday. The effort was his best of the season after going 7-8 with a 5.61 ERA in 24 starts for the Red Sox.
"I just think this guy was on a mission and it showed," Bochy said. "Some things are hard to explain."
Penny hopes the change of scenery will help turn around a dismal season.
San Francisco (75-62) is 5 1/2 games behind NL West-leading Los Angeles, but two back of wild-card leader Colorado. The Giants face both clubs on this homestand.
"This is what you put a uniform on for, to get into the playoffs and play in the World Series," said Penny, who won a World Series with Florida in 2003.
Penny, however, hasn't fared well against the Padres, going 3-8 with a 5.66 ERA in 16 lifetime starts, including 0-4 in his last seven since beating San Diego in 2005.
The Giants hope to bounce back from a 2-1, 12-inning loss at Milwaukee on Sunday that concluded a 3-3 road trip.
"There's no room right now for dwelling on stuff, because the season is winding down and you have to concentrate on the next day," center fielder Aaron Rowand told the Giants' official Web site.
Pablo Sandoval drove in the lone run for San Francisco, which scored 12 runs on the trip. The third baseman is batting .467 with two home runs and seven RBIs in his last four games against San Diego.
The Giants could get a boost with second baseman Freddy Sanchez likely available for the first time since going on the disabled list with a shoulder strain on Aug. 18. Sanchez is batting .304 in 13 games since being acquired in a trade with Pittsburgh.
Though the Giants are 5-7 against the last-place Padres (61-77), they've won nine of 10 at home versus San Diego.
Despite their struggles this season, the Padres have won nine of 12 overall after beating Los Angeles 4-3 on Sunday to take two of three from the division leaders.
"I want the opposition to know that when we take the field against them, they're in for a good ball game," Padres manager Bud Black said.
Adrian Gonzalez hit his 35th homer - one shy of matching his career high from 2008 - and Kevin Kouzmanoff had three RBIs for the Padres, who've won six of nine on the road.
Though Gonzalez is batting .217 without a homer versus the Giants this season, the All-Star first baseman is hitting .353 against Penny.
Clayton Richard (4-1, 4.50) looks to win his second straight start while making his first against San Francisco in this contest.
The left-hander allowed one run and four hits in 6 2-3 innings of a 4-1 win over Washington on Tuesday in one of his better outings since coming over from the Chicago White Sox in the Jake Peavy trade on July 31.Sign up for breaking news alerts from FOXSports.com!