Giants 5, Rockies 3: Hunter Pence hit the longest home run in the major leagues this season and Yusmeiro Petit pitched six solid innings as visiting San Francisco defeated Colorado.

Pence hit a 476-foot, two-run homer in the first inning that cleared the left-field bleachers and Pablo Sandoval followed with a solo shot as the Giants evened the series at a game apiece. Brandon Belt went 4-for-5 and Sandoval finished with three hits.

Petit (1-0) struck out six while allowing two runs and six hits en route to his first major-league victory since 2009. Three relievers bridged the gap to Sergio Romo, who worked a perfect ninth for his 32nd save in 36 opportunities.

San Francisco had a quick 3-0 lead due to Pence’s mammoth blast off Chad Bettis (0-3) and Sandoval’s ensuing homer to left-center field. Colorado got on the board in the third, when Nolan Arenado singled and scored on Charlie Blackmon’s double over the head of Giants center fielder Gregor Blanco.

The Rockies cut the deficit to 3-2 on Wilin Rosario’s RBI single in the fourth. San Francisco padded the lead on a run-scoring single by Hector Sanchez in the sixth and a sacrifice fly by Marco Scutaro in the seventh before the Rockies recorded a seventh-inning run on DJ LeMahieu’s groundout.

GAME NOTEBOOK: Rockies SS Troy Tulowitzki (ribs) returned from a two-game absence and went 1-for-3, while CF Dexter Fowler (knee) sat out. … C Sanchez went 2-for-4 while playing in place of a resting Buster Posey. … Bettis allowed four runs and nine hits in six innings.