BOSTON (AP) — Mike Yastrzemski had a visit from his grandfather Carl and then homered into the Red Sox bullpen like the Hall of Fame outfielder so often did in his heyday, and the San Francisco Giants beat Boston 3-1 on Thursday. Ryan Walker (3-2) pitched a perfect sixth inning to help the Giants avoid the sweep and snap Boston’s four-game winning streak. Camilo Doval pitched the ninth for his sixth save. “Six hits. Scratched three runs out of it today, but there’s still more out there,” said Giants manager Bob Melvin, whose team had just 15 hits in the three-game series. “But when you win a game you don’t really concern yourselves with that. It’s when we’re losing games and not get many hits and not scoring many runs. Did enough today.” Tyler O’Neill walked twice and hit a wall-scraping popup to drive in Boston’s only run. Carl Yastrzemski visited his grandson in the visitor’s clubhouse before the game, but did not stay to see Mike come up in the third inning of a scoreless, hitless game and line a 1-1 pitch from Josh Winckowski over the short wall in right field. Although there were plenty of Giants fans in the crowd for the team’s first trip to Boston in five years, even the Red Sox fans stood and cheered for the opponent with the familiar last name.