The Post Sports Live crew discusses whether manager Davey Johnson bears the responsibility for the Nationals’ slow start to the season. (Post Sports Live)

When good baseball teams get away from their core identities and inexplicably play as if they have been inhabited by alien beings, one clue often solves the mystery: They are focused on instant results rather than the process of playing properly. They constantly try to win the game rather than to simply make the next play or pitch that leads, eventually, to good results.

Everybody in baseball knows this. Yet in any season, every team loses itself at least once, often for weeks at a time, and has to find its way back.

For three weeks, the Washington Nationals have wandered in this desert. Stephen Strasburg lost three in a row and said he was “trying to do too much.” Ryan Zimmerman tried for “a perfect throw” on an impossible play and threw the ball away when, in hindsight, holding the ball would have won the game.

Perhaps the Nats reached their nadir of mental mistakes, errors on basic plays, baserunning gaffes and pitchers trying to be “too fine,” when Jayson Werth swung at a 3-0 pitch and grounded into a double play Sunday.

“One of the dumbest things I’ve done in a long time,” Werth said. After that loss, the Nats took stock and reached the same conclusion every team does (until the next time they forget it): Play the game right, let the score take care of itself. Now, they are working their way back toward themselves.

How long will it take?

Wrong question!

See, that’s the problem. Impatience is so ingrained in our nature that it’s hard to think of the word “improve” without jumping straight to “win.” The process of the Nats playing sound ball again will take as long as it takes.

With 26 of the next 36 games against good-to-excellent teams, the Nats may play better yet have a record that resembles their current 10-10. But at least they’ve started the process of self-awareness after weeks, not months.

“This was a huge step in the right direction. Everyone played a good game even though they beat us by a run,” Ian Desmond said after Monday’s 3-2 loss to St. Louis. “We didn’t beat ourselves.”

But fans will say that you lost anyway, and to the same Cardinals team that eliminated you from the playoffs last year, Desmond was told.

“That’s why they are fans, and we are players,” the 2012 all-star said.

Big leaguers seldom say it so directly, but that’s dead right. Players, when functioning best, think like athletes: focusing on details. When they play worst, they are thinking like fans: Are we winning, panicking, choking?

So far, the Nats have played like emotional-roller-coaster fans. They’re lucky to be 10-10.  Their two best-played games of the season — for pitching, defense and zero mental mistakes against a gifted club — may have been their two losses to the Cards this week, including a 2-0 defeat Tuesday night; that’s a back-handed compliment at best. Their ugly run differential (74-91) says they deserve to be 8-12, akin to the Angels (7-11), Blue Jays (8-13), Dodgers (9-10) and Tigers (9-9). What do those teams have in common? They were the five top picks to win the World Series in the final preseason odds.

High expectations are the most likely culprit. Like any team, the Nats deny it. “We’re not trying to win the World Series in April,” Desmond said.

You can’t prove that preseason pressure has distracted the Nats. But why bother? Whether the Nats’ play was caused by Favorite Fever or phases of the moon makes no difference. The symptoms, and the cure, are the same.

“This is a good spell for us: nothing but good clubs,” Manager Davey Johnson said. “We’re going to have to play. We can’t be thinking about nothing.”

Nobody knows better than Johnson that thinking and playing baseball cannot be done simultaneously. Thinking prepares you to play. But in the moment, you must be spontaneous, almost unconscious, and enjoy your gift.

More than any Nat, Dan Haren is in the midst of analyzing the sport between games, but trying to relish it when he’s actually pitching — no easy task when you have given up 32 hits in 181 / 3 innings.

After a winter of rehab exercises prescribed by the Nats, Haren’s velocity was back to 90.4 mph Monday, right in the middle of his 2009-11 norm and better than any game of ’12 when he averaged 89.5. That should spell success and perhaps a free agent steal by the Nats. But it hasn’t.

Haren’s first three awful starts epitomize the desire to win, prove he’s “back” and vindicate his $13 million contract rather than pitch in the brainy precise way that defined him his whole exceptional career. Now, Haren concedes he fell too much in love with his good health and revived fastball.

“I was throwing more than 50 percent fastballs,” he says sheepishly, knowing he was at 34 percent in ’11. Haren even threw his cutter too hard, erasing much of the gap in speed between it and his fastball while also decreasing his cutter’s late break. He had to throw it slower, locate better.

In his fourth start, he did, sort of, with five fine innings but a bad sixth. Haren has turned a corner, but that too is a process, not an instant correction.

“I’ve felt really good, so losing has been eating at me; it really has,” Haren said. “I told myself, ‘Have more fun’ rather than stress too much.”

As he said it, the lights in the Nats’ clubhouse flickered, and half of them went out. Haren continued his interview, saying, “Baseball will humble you.” At that, the rest of the lights went dead. The room was black. The Nats had just lost to the same team that turned out the lights on their ’12 season.

Nervous chuckles. In a minute, the lights came back on. Choose your symbolism or ignore it. The Nats briefly lost some of their luminous aura, but have they now glimpsed the necessary humility they may have misplaced?

For months, the Nats have been listening, talking and thinking about many distracting things: Game 5, the Cardinals, “World Series or Bust.”

This week, they came full circle. On Monday, the Nats were reunited with Pete Kozma and 10/12/12 was recapitulated. They saw Kozma single to right, get intentionally walked by Johnson with the pitcher on deck and face Drew Storen again but, this time, strike out. Is baseball a stand-up comic? The game must stay up all night thinking of ways to get in players’ heads.

A player’s job is not to allow it or, at least, not for too long.

Isn’t it time for the Nats, distracted by both past and future, to grasp the present and say, “We can’t be thinking about nothing” except the game?

The Nats actually say they have made that decision. How well and how soon that process produces results is a mystery.

When do the lights come back on?