SAN DIEGO — Perhaps it has been just a matter of repetitions. After all, the Mets have faced only four lefthanded starters this season. But whatever the reason for their struggles against southpaws, the Mets need to find an answer soon.

The Dodgers are scheduled to throw three lefties — including the great Clayton Kershaw — in a four-game set that begins Monday night.

“The more you see, the more you get used to it; guys get into more of a better rhythm against lefthanded pitching,” manager Terry Collins said.

The Mets have scored only three runs in 23 1⁄3 innings against the four lefthanded starters they have faced this season: Brandon Finnegan, Madison Bumgarner, Adam Conley and Drew Pomeranz.

“I think it helps a lot to see two lefties in a row and to get five, six, seven at-bats against them,” said switch-hitting second baseman Neil Walker. “It lets you kind of breathe a little bit, it lets you not be so defensive. Ultimately, you tend to be more productive when you’re up there not just trying to see the ball.”

Collins has used games against southpaws to give at-bats to his bench players, though with only mixed results.

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Entering Saturday night, Juan Lagares was 6-for-17 (.353) against lefthanded pitching this season and appears to have adjusted to fewer at-bats with Michael Conforto, Yoenis Cespedes and Curtis Granderson taking most of the playing time in the outfield.

But Wilmer Flores has languished in his new role as a backup infielder. Though he has shown signs of life lately, he was hitting only .179 before Saturday night’s game. Lefties gave Flores no problems last season, but he’s 1-for-12 against them in 2016.

“Those kinds of guys, they’ve got to do the damage against [lefties],” said Collins, noting Flores’ work against them in 2015. “Somebody’s got to step up and get some big hits.”

Of course, some of the Mets’ better hitters traditionally have struggled against lefties, including Curtis Granderson and Lucas Duda.

“We have guys that don’t necessarily have great numbers against lefthanded pitching,” Collins said. “That’s just the nature of the game, but that’s some of the guys that we have. So what you try to do is pick your spots for when you try to get those other guys a game here and there.”