By JON PALMIERI
(AP) -- It's likely only a matter of days before the San Francisco Giants clinch their second NL West title in three seasons.
While that appears to be a foregone conclusion, Ryan Vogelsong's struggles are much harder to define.
The Giants hope to inch closer to the division title and see improvement from Vogelsong on Friday night in the opener of a three-game set against the visiting San Diego Padres.
San Francisco (87-63) continued its blistering pace with a 9-2 victory over Colorado on Thursday to complete a four-game sweep. Pablo Sandoval homered from both sides of the plate and Buster Posey also connected as the Giants won for the eighth time in nine games and reduced their magic number for the West crown to three.
"The view looks great right now," center fielder Angel Pagan said. "We have to really make sure. We can't talk about playoffs right now."
With a 10-game lead over Los Angeles, San Francisco could wrap up the division as early as Saturday. The Giants are 24 games above .500 for the first time since ending the 2003 season 100-61.
Sandoval went 8 for 16 with three homers and seven RBIs in the sweep after going 5 for 35 in his previous nine contests.
"I'm comfortable at home plate. I don't try to hit home runs," said Sandoval, who snapped a homerless drought of 161 at-bats Wednesday night. "When you don't try, things go your way. I got lucky, man."
While San Francisco's rotation has performed very well lately, Vogelsong (12-9, 3.65 ERA) has been the exception. The right-hander has a 10.31 ERA over his last seven starts, contrasting with an NL-best 2.27 ERA in his first 21 outings.
Vogelsong lasted only 3 1-3 innings for the second time in three starts, allowing seven runs and five hits in a 10-2 loss at Arizona on Sunday.
"The balls came out good that is why it is getting perplexing," he said. "My stuff is there. It just doesn't make much sense right now."
Vogelsong has given up 20 runs in his last four starts with opponents batting .360 during that span.
"His stuff is good, he is just going through a tough period," manager Bruce Bochy said. "He has been through it before and he will come out if it."
San Diego (72-78) avoided a three-game sweep at Arizona with a 6-5 victory Thursday, getting a three-run homer from Jesus Guzman before Anthony Bass worked out of a bases-loaded jam in the ninth for his first career save.
Looking to continue in the role of spoiler, the Padres send rookie Casey Kelly (2-1, 5.85) to the mound.
The right-hander rebounded from a pair of disappointing performances with a strong showing in a 4-3 victory over Colorado on Saturday. He carried a shutout into the seventh inning before allowing three runs - two earned - and seven hits over six-plus. The 22-year-old didn't walk a batter for the second consecutive start and struck out a season-high six.
"You get more and more comfortable every time out there," Kelly said. "Every inning you get you feel more comfortable with the team. I think every outing is just getting more and more comfortable."
Kelly surrendered 13 runs - 11 earned - and 16 hits in his previous two starts over eight innings after tossing six scoreless to win his major league debut Aug. 27.
San Francisco has won eight of 12 against San Diego this season, including four of six at home.
Updated September 20, 2012