SAN FRANCISCO (AP) — Rookie Christian Arroyo homered, Brandon Belt had three hits including a double, and the San Francisco Giants beat the San Diego Padres 4-3 on Friday night.Arroyo, playing in his fifth game since being called up on Monday, homered for the second time in three games leading off the bottom of the eighth inning off Ryan Butcher (1-1).Joe Panik made a diving over-the-shoulder catch on Yangervis Solarte’s popup in short center field for the first out in the top of the ninth as Mark Melancon pitched a scoreless inning for his fifth save.Derek Law (3-0) worked a scoreless eighth.Giants starter Jeff Samardzija had lost all four of his previous starts and took the National League’s worst ERA into Friday. He had a 3-0 lead and hadn’t allowed a hit going into the top of the fifth before serving up a two-run home run to Ryan Schimpf, who homered for a third straight day.Schimpf was 1 for 28 before starting the homer streak on Wednesday. His sixth home run cleared the 399-foot sign in center field, landing in AT&T Park’s vegetable garden.Luis Perdomo allowed three runs (one earned) on six hits in six innings in his second start since coming off the disabled list with a shoulder injury.TRAINER’S ROOMPadres: RHP Jarred Cosart on Saturday will throw his second bullpen session since going on the disabled list with a hamstring injury earlier this month, manager Andy Green said.