Law tweaks his repertoire

Early this season, batters loved facing Giants reliever

Derek Law, whose slider and curve were roughly the same speed and broke roughly the same way.

“They could sit on basically the same pitch,” Law said Friday after rejoining the Giants as part of the first wave of September call-ups.

After Law posted a 2.13 ERA as a rookie, the Giants expected him to be the primary setup man, but they had enough of his 5.40 ERA through mid-June and optioned him to Triple-A Sacramento.

Out the door, he heard from catcher Buster Posey, who suggested he work on differentiating his pitches. His slider was in the 78-79 mph range, not a far cry from his 75 mph curve.

Law tweaked his mechanics and grip and added velocity to his slider, which now is well into the 80s, closer to what it was last season.

“When I caught him his first couple of outings, honestly, the pitches looked the same,” said catcher Tim Federowicz, who also was called up Friday. “He’s actually got two distinct pitches, different speeds, different actions. The slider is harder and tighter.”

Law’s ERA at Sacramento was 2.48, and he earned 10 saves. Initially with the Giants, he’ll be used in the middle innings. He appeared Friday night against St. Louis, getting his only batter, Yadier Molina , to line out on three pitches to end the top of the sixth inning.

Melancon surgery: Closer Mark Melancon, who twice spent time on the disabled list with a pronator strain, could be shut down soon to undergo season-ending surgery.

Manager Bruce Bochy said recovery would take six to eight weeks, so being ready for spring training shouldn’t be an issue.

Melancon, who signed a four-year, $62 million contract in the offseason, has a 3.95 ERA in 29 games. He hasn’t appeared in a save situation since June 20.

He gave up the tying run while pitching the eighth inning Friday night.

More roster news: The other player called up from Sacramento was lefty Steven Okert. Utility man Orlando Calixte is expected to be called up in the next couple of days. Third baseman Jae-Gyun

Hwang was outrighted off the 40-man roster for Federowicz, meaning Hwang won’t join the Giants in September.

“I like Jae and appreciate what he’s done,” said Bochy, noting there’s little room at the corners with Pablo Sandoval at third and rookie Ryder

Jones at first.