(Jonathan Newton / The Washington Post)

Adam LaRoche, 33, has played baseball for a lifetime, the past nine years in the major leagues. Entering Friday’s game, he had 4,739 major league plate appearances under his belt. But even with all that experience, when a slump hits, one that isn’t mechanical or physical, he can’t explain it. The rule of thumb is simple: “You just swing through it,” he said.

LaRoche, who carried the Nationals‘ offense at times last season and finished with 33 home runs and 100 RBI, is mired a season-starting slump. He is a notoriously slow starter; his career OPS in April is the lowest of any month of the season. Nonetheless, he is frustrated with his .159/.243/.317 production line in 19 games. Earlier this season, he was hitting the ball hard and his average didn’t reflect it. Now, he is missing. Over the past seven games, he is 2 for 22 and was given a game off by Manager Davey Johnson to get a mental break.

“I’ve talked to a lot of good hitters over the years and never found the perfect solution for getting out a funk other than swing,” said LaRoche, whom the Nationals re-signed this winter to a two-year, $24-million deal. “Let it run its course and don’t let it get too mental and just swing. If you’ve done something that’s successful and you know it’s successful then continue to work through it. I think it’s different for guys trying to find their way and don’t know for sure what works or doesn’t work then you make adjustments. I go back and watch film or when things are going well and you put those side by side there’s no difference, then you just keep swinging.”

LaRoche and hitting coach Rick Eckstein have examined the left-hander’s swing and neither has noticed any physical or mechanical issues. Johnson believes LaRoche will pull out of his slump soon. (“His approach is good. He’s a veteran hitter. He’s going to be fine. This is more normal stuff he’s gone through in the past,” he said.) At-bats just feel more difficult when a batter is in a slump — missing pitches you’d normally crush, every appearance feels like it start 0-1 and opposing pitchers feel like Cy Young.

“All that falls into place when you’re rolling,” LaRoche said. “That’s why it’s one of the trickiest things in sports to explain. I don’t know.”

With so many factors and moving parts, hitting, like pitching, is about feel. And right now, LaRoche doesn’t feel it. (He compared the feeling to hot and cold stretches in golf.) But sometimes it takes just one good at-bat or series of at-bats to snap out of it. LaRoche’s career OPS in April is .708, jumps to .763 in May and .771 in June and keeps climbing until August.

“It’s crazy, you think after 10 years I’d have a more complex answer” for the slump, he said. And as a result, it’s a little frustrating to have so much experience and still slump. “On the other hand, you’ve been there before and know the process of it and not to freak out and snowball into something bigger,” he said.