Pirates 10, Giants 5: Jose Tabata’s bases-clearing double capped a seven-run rally in the fifth inning and visiting Pittsburgh won the opener of the four-game series.

Garrett Jones and Jordy Mercer added solo homers for the Pirates, who maintained their one-game lead over St. Louis in the National League Central. The Giants fell to last in the NL West while being outscored 31-9 over their last four games.

Guillermo Moscoso (1-2) began the fifth inning by hitting Tabata and walking the next two batters before Pedro Alvarez broke a 3-3 tie with a ground-rule double off Jose Mijares. Jeanmar Gomez (3-0) tossed three scoreless innings after Jeff Locke yielding three runs over four innings.

Giants starter Matt Cain left the game with one out in the fourth inning after taking a line drive off his pitching arm, but X-rays were negative and he was diagnosed with a right forearm contusion. Cain allowed three runs on seven hits over 3 1/3 innings after holding the Pirates to a 1.24 ERA over his last six starts.

Andrew McCutchen had two hits and reached base four times for Pittsburgh, which has won three of its last four games. Brett Pill collected three hits and Marco Scutaro and Brandon Crawford each had two RBIs for the Giants.

GAME NOTEBOOK: McCutchen has hit safely in each of his last nine games against San Francisco. … The Giants placed OF Andres Torres on the 15-day disabled list with a left Achilles strain and optioned LHP Mike Kickham to Triple-A Fresno and recalled OF Francisco Peguero and INF Nick Noonan from Fresno. … Giants 3B Pablo Sandoval returned after missing two games with a sore back and had a single in three at-bats.