SAN FRANCISCO -- The Dodgers bolted from the starting gate with a 20-12 record over March and April, but they began May with a 2-1 walk-off loss in the ninth inning to the Giants on Wednesday night that exposed their most obvious weakness.

They are 15-8 in games started by opposing right-handed pitchers, but only 5-5 in games started by opposing left-handed pitchers, like the Giants’ Madison Bumgarner, who allowed the Dodgers one run over six innings.

And if there is a left-handed hitter who typifies the Dodgers’ struggles right now, it’s Corey Seager.

Dodgers starter Hyun-Jin Ryu outpitched Bumgarner and went eight innings, but for the first time this year, the Dodgers lost despite getting a quality start. Julio Urias and Pedro Baez combined for a defeat that might not have been if Dodgers hitters had done better than 1-for-10 with runners in scoring position, stranding eight.

So, the first-place Dodgers lost two of three to the last-place Giants and will find opposing teams looking high and low for left-handed pitchers to send against them, beginning this weekend when the Padres start a trio of them -- Eric Lauer, Joey Lucchesi and Nick Margevicius.

After trading right-handed-hitting outfielders Yasiel Puig and Matt Kemp during the winter, the Dodgers signed A.J. Pollock to provide right-handed balance, but he’s out indefinitely with elbow surgery scheduled for Thursday. David Freese, re-signed in the winter to be a force against lefties, was a late scratch after bruising an ankle on a foul ball the night before. He’s expected back by Friday.

But for Wednesday night, manager Dave Roberts had four left-handed hitters -- Seager, Cody Bellinger, Max Muncy and Alex Verdugo -- in the starting lineup. They went 2-for-14 against Bumgarner and left-handed relievers Tony Watson and Will Smith.

A hustling Bellinger had the only RBI on an infield single in the sixth inning, although it was Enrique Hernandez who was running on the pitch and scored the tying run from second base.

Seager, meanwhile, went 0-for-4 with three strikeouts. He is batting .228 overall, .154 against left-handers and looks as rusty as one would imagine for a player who missed most of last year with Tommy John elbow reconstruction, followed by serious hip labrum surgery, and was rehabbing in Spring Training.

In typical fashion, Seager downplayed the notion of rustiness.

“There’s some things that are not where I’d like them to be,” said Seager. “I don’t want to blame it on that [rustiness]. I’m not where I should be. You obviously knew I would need some ABs. Been a long time, really long time, since I played every day and faced tough pitching.

“Just kind of searching a little bit, but I’m not far. Missing a few little things. I look for mechanics most of the time. There’s a few things that are off I’m trying to work through. What I’m doing wrong makes it a little tougher on the left-handed angle. It’s frustrating, yeah.”

Manager Dave Roberts said Seager’s problems are mechanical.

“When you’re not going well, balls that could go either way go against you, and balls he should handle he’s missing them,” he said. “It’s a little combo. Corey, it’s one of those things where you just keep running him out there. He’s too good a player not to turn it around.”

The struggles of the Dodgers offense wasted a stellar start from Ryu, who allowed one run on four hits (two left the infield), struck out six and again didn’t walk any over eight innings. He has 39 strikeouts and only two walks this year.

But with Scott Alexander unavailable because of a tight hamstring, Roberts turned to Urias, who allowed a pair of ninth-inning hits. With two outs, Baez came on to face Buster Posey, whose single to left on a 3-1 pitch scored Steve Duggar just ahead of left fielder Chris Taylor’s throw. That tied Matt Williams for the most San Francisco walk-off plate appearances (three) against Los Angeles since the teams moved to California.