The Diamondbacks, who have won the division on four other occasions, enter this series with a six-game lead on the Giants and a magic number of one for clinching their first title since 2007.
Arizona won for the third time in four tries on Wednesday, beating the Pittsburgh Pirates 8-5. The win was the 90th on the season for the Diamondbacks, who lost 97 games a year ago and finished last in the National League West.
J.J. Putz picked up his 22nd straight save in the win, as Arizona reached the 90-win plateau for the fifth time in franchise history.
While a division title is almost a certainty at this point, the Diamondbacks are also just a game back of the NL Central-leading Milwaukee Brewers for the second-best record in the league and home-field advantage in the best-of-five NL Division Series.
"Let's just get there. I'm focused on getting there," said Gibson when asked if he would rest some starting pitchers and position players after the team clinches. "We're one back of Milwaukee now, right? We'd like home-field advantage. We play pretty good here. I'd like to bring the playoffs here to our fans, get some excitement going on."
Heading to the hill for Arizona tonight will be left-hander Joe Saunders, who has won his last three and four of his last five starts. Saunders beat the San Diego Padres on Sunday, holding them to just an unearned run in 8 2/3 innings, as he improved to 12-12 on the year to go along with a 3.66 ERA.
Saunders, though, has lost all three of his starts to the Giants, while pitching to a 5.21 ERA in those outings.
San Francisco, meanwhile, comes into tonight's tilt on the heels of a back- breaking loss to the Dodgers, as the Giants severely hurt their postseason chances with Thursday's 8-2 setback.
In addition to the division deficit, the loss in the rubber match of the three-game series dropped the Giants four games behind the NL wild card- leading Braves
"We dug this hole," manager Bruce Bochy said. "We knew what was ahead of us. Now we realize we can't lose a game. But you still should enjoy it, because you're playing meaningful games."
San Francisco will rely on righty Matt Cain, who is 12-10 with a 2.86 ERA. Cain defeated Colorado on Sunday, limiting the Rockies to five runs (three earned) and five hits in five innings.
Cain has faced the Diamondbacks 22 times and is 10-5 against them with a 3.45 ERA in 22 starts.
San Francisco is 9-6 against the Diamondbacks this season.