It was 5-5 when Josh Bell opened the eighth with a double and moved to third on Corey Dickerson's groundout. Watson intentionally walked Francisco Cervelli, and pinch hitter David Freese loaded the bases with an infield single.

Watson (1-2) then hit Mercer in the left leg to bring home Bell.

San Francisco has lost a season-worst six straight.

Pirates starter Chad Kuhl gave up three runs and six hits in six innings, with six strikeouts and four walks. Closer Felipe Vazquez (2-0) got the final five outs.

San Francisco starter Jeff Samardzija had his longest outing of the season, allowing five runs and six hits in 5 2/3 innings, with five strikeouts and two walks.

After the start of the game was delayed about 90 minutes by rain, the Pirates took a 2-0 lead in the first on Bell's sacrifice fly and Corey Dickerson's RBI single.

San Francisco tied it in the second. Evan Longoria hit a first-pitch home run, his eighth, to left-center to make it 2-1. One out later, Alen Hanson hit his fourth homer, a line drive to right, to make it 2-2.

The Giants took their first lead of the series in the third when Andrew McCutchen led off by stretching a single into a double and later scored on Brandon Crawford's sacrifice fly, making it 3-2.

Gregory Polanco planted a ball just over the wall in right-center, his eighth homer, with one out in the third for a 3-3 tie.

Cervelli hit a two-out, two-run homer in the sixth after Bell reached on a base hit for a 5-3 Pirates lead.

In the seventh, McCutchen hit a one-out double and scored on Brandon Belt's two-out single to pull the Giants to within 5-4.

In the eighth, Austin Jackson tied it 5-5 with a double off the wall in left, driving in Hanson, who had a one-out single. Hanson left the game after scoring because of an unspecified injury he apparently suffered running the bases.

--Field Level Media