SAN FRANCISCO (Ticker) -- A year ago, the San Francisco Giants watched the Arizona Diamondbacks clinch the National League West title at Candlestick Park. Tonight, in their new ballpark, the Giants did all the celebrating.

San Francisco captured its second NL West crown in four years with an 8-7 victory over the reeling Diamondbacks as pinch-hitters Russ Davis and Felipe Crespo drove in key runs in the bottom of the eighth inning.

Davis' sacrifice fly snapped a 6-6 tie and Crespo's single plated a much-needed insurance run for the Giants, who recorded their earliest clinching since 1954, the year they last won the World Series.

Closer Robb Nen, who had not allowed a run since July 13, gave up a two-out RBI double to Danny Bautista in the top of the ninth. But he retired Jay Bell on a long fly ball to center fielder Calvin Murray, who pumped his fist after the catch, setting off a wild celebration.

Fans waved white towels while some Giants crowded around Murray and others mobbed Nen.

It was appropriate San Francisco won the clincher at Pacific Bell Park since they own baseball's best home record at 54-23. The Giants lost their first six home games before turning things around with a four-game sweep of the New York Mets in the first week of May.

Doug Henry (4-4) pitched two hitless innings to win the clincher and a shaky Nen got his 39th save in 44 chances despite allowing a run for the first time in 27 outings.

The loss went to reliever Mike Morgan (5-4), who gave up two runs and two hits in 1 2/3 innings.

Arizona, the defending NL West champion, has dropped six straight, all but destroying its postseason hopes. The Diamondbacks are six games behind the New York Mets in the wild card race but must leapfrog the Los Angeles Dodgers, who completed a three-game sweep of Arizona on Wednesday.