Giants get two homers from Belt, including slam, but lose again

At Petco Park on Friday, Brandon Belt hit his first grand slam in 2,375 major-league at-bats on a two-homer day, yet they lost again.

Belt's sixth-inning grand slam off Luis Perdomo converted a bad Matt Cain start into a 5-4 lead, which disappeared at the hands of George Kontos in a three-walk, three-run seventh inning.

By the time Cain trudged off the mound with one out in the fifth inning, a run and the bases loaded, Margot had two homers and the Padres a 4-1 lead.

After Bumgarner had a fine Opening Day, holding the Diamondbacks to three earned runs in seven innings, Johnny Cueto, Moore, Samardzija and Cain combined to allow 17 earned runs in 20 innings.

Cain's line might have looked worse if not for still-hitless Jarrett Parker running down second-inning drive into the right-field corner by Perdomo to end the second inning and strand two runners.

Cory Gearrin kept the Giants in the game when he relieved Cain with the bases loaded in the fifth and got Austin Hedges to ground into a double play and keep San Diego's lead from growing beyond the reach of a grand slam.

The offense grabbed the reins in the next half inning and finally hurt Perdomo, the Pads' No. 5 starter.

Belt, who had a double, triple and homer in Arizona, got ahold of an 0-1, do-nothing curveball and powered it into the right-center seats where the sandbox used to be.

The Giants might have given Cain the fifth spot in the rotation out of spring training, but his hold on the job is hardly secure with Ty Blach on the roster, Tyler Beede in the wings and two off days coming after the first homestand

When Cain took the mound, the became the fifth pitcher in franchise history to start at least one game in 13 consecutive seasons.

[...] Bochy had to act after Solute's second RBI single, a walk and an Eduardo Nuñez error loaded the bases with one out in the fifth.