Ty Blach went seven shutout innings Sunday, but Mark Melancon blew the save in the ninth and the Padres went on to beat the Giants 5-2 in 12 innings.
Wil Myers again hurt the Giants as he hit a go-ahead three-run homer off George Kontos in the top of the 12th.
Blach, filling in for the injured Madison Bumgarner, gave up three hits and walked two. He struck out just one batter.
The rookie pitcher's sacrifice fly in the bottom of the fifth gave the Giants a 1-0 lead.
Michael Morse drove in Hunter Pence with a double in the sixth to boost the Giants' lead to 2-0.
With one out and one on in the top of the ninth, Melancon gave up a game-tying two-run homer to former Giants catcher Hector Sanchez.
The Giants designated right-handed reliever Neil Ramirez Sunday and purchased the contract of right-handed reliever Bryan Morris from Triple-A in a corresponding move, the team announced.
Ramirez appeared in nine games for the Giants this season. In 10.1 innings pitched, he went 0-0 with a 13.06 ERA.
Morris has spent time with both the San Jose Giants and Sacramento River Cats this season. Between the two levels, Morris is 1-0 with 0.00 ERA in five games.
The 30-year-old fractured his right foot in spring training during a live batting practice drill. Over five years in the majors, Morris is 18-12 with a 2.80 ERA.
Neil Ramirez designated for assignment. Right-hander Bryan Morris called up from Triple-A.— Alex Pavlovic (@PavlovicNBCS) April 30, 2017