Denard Span and the Nationals suffer a stunning defeat that sends them staggering into Atlanta for a three-game series against the division-leading Braves. (Ricky Carioti/Washington Post)

“That one hurt,” Manager Davey Johnson said, almost unable to find additional words after closer Rafael Soriano, just one strike away from victory, served up a two-out full-count game-losing three-run homer to obscure Giants pinch hitter Hector Sanchez on Thursday at Nationals Park.

“It definitely hurts,” said starting pitcher Dan Haren, whose win was blown as well as what would have been the Nats’ sixth straight victory.

You never know which wound will strike a vital organ. You never know which loss will be the final unhinging of a season. For the Nats, who had gotten to one knee in the last week, regaining a bit of dignity, this was a blow that sent them sprawling again. This 4-3 loss came at the worst time, heading to three games in Atlanta against the Braves who have thumped them in 10 of 13 meetings and lead them in the NL East by 141 / 2 games.

“The mood kind of stinks right now in here,” Haren said in the silent locker room after his seventh effective start (2.30 ERA) since coming off the DL. “But we can’t go to Atlanta feeling sorry for ourselves or we’re going to get rolled.”

In a brutal Nats season, this was another gruesome day. The pitch before Soriano’s gopher ball to the .213-hitting Sanchez was a strike, that should have ended the game, according to PITCHf/x, the most accurate measuring device MLB possesses. It nicked the zone, letter high, by perhaps an inch. But PITCHf/x doesn’t have a right arm to raise. It’s just a machine.

The umpire, in this case Jim Joyce, owns the strike zone and calls it his way. If he’s consistent, he’s a good ump. Even Johnson didn’t question his call. “He called the low strike all day [not the high strike],” Johnson said. “What [got us] was walking the left fielder [Roger Kieschnick, the previous hitter] . . . You gotta get him out or make him put the ball in play. Some guys, you have to say, ‘Here, hit it.’ ”

Walking rookie Kieschnick, who’s never had an extra-base hit in the big leagues, was the original sin. Sanchez’s home run — only his fourth in 297 big-league at bats — was just the appropriate punishment.

In baseball, as in childhood, growing up takes years. Maturity is easy to praise, hard to acquire and usually involves a cruel word: experience. They tell you to learn from the mistakes of others, rather than enduring all of that harsh experience yourself. But they never tell you exactly how to do it.

So, time after time, that experience arrives on days like this. The Nationals seem determined to have every single kind of elation and exasperation on the baseball spectrum on the winding trail to wherever they are ultimately headed as a baseball destiny.

They have gone from 103-loss awful to decent, then from decent to excellent in one huge gulp last year, then from excellent to a preseason World Series favorite with all the pressure of expectations. And now they enter a new and also educational stage. They are the bitterly disappointed team that has been written off, its postseason chances down to about 2 percent, that has suddenly gotten hot; but, at the same time, they can hardly afford a single misstep if they are to keep their slim wild-card chance alive.

Now, the Nats get to be the chaser, the hunter, the zombie team. In one sense, it is the hardest task in baseball because, statistically, it is so improbable that you will succeed. Games like this show why.

But psychologically, it may be the easiest job in the game. You’re already dead. What do you have to lose? You show up, play with intensity. That desperate sense of urgency focuses almost every athlete in every sport. And, usually, it frees them. As if to offer an illustration, before this game Cal Ripken Jr., caught the ceremonial first pitch. In his rookie year in ’82, the Orioles were as close to pennant-race death as the Nats are now. But after Aug. 19, the O’s went 33-10 to catch Milwaukee with one day left in the season. They lost that final game. But it shows what’s possible.

Those O’s had “that one hurt” defeats that almost derailed their streak. Twice Scott McGregor was knocked out without recording a single out.

How will the Nats react to this latest blow? Perhaps they need the perspective of their setup man Tyler Clippard (2.03 ERA) who pitched ascoreless eighth inning. “This year has been so hard,” he said. “But it is all part of a process that you can’t escape.”

Clippard looked around the clubhouse at the players he has known in his six seasons in D.C. Next to him was his best friend, Drew Storen, just called back on Thursday from Class AAA Syracuse, where he’d spent three shocking weeks fixing his pitching mechanics to restore a career that saw him save 43 games in ’11.

Everywhere Clippard looked he saw illustrations of “baseball experience” and just how painful that education actually is. “This is what you have to go through to grow up in this game,” he said. But he shook his head as he said it. Sometimes it’s hard to digest the game’s casual malice.

Danny Espinosa, Tyler Moore and Ryan Mattheus, valuable last year, are all at Syracuse getting their careers out of the ditch. Across the room, Jordan Zimmermann and Stephen Strasburg are pillars of the staff, but both missed a year with elbow surgery. Ross Detwiler is out for the year with a bad back.

Catcher Wilson Ramos has missed 216 games the last two years. Ryan Zimmerman has battled wild throws on routine plays for three years. Chad Tracy, Roger Bernadina and Steve Lombardozzi, part of the praised Goon Squad of ’12, have hit so poorly that all their futures are in various stages of doubt. Rookie Anthony Rendon, forced to play a new position, has 12 errors in only 67 games. Denard Span, who made a game-saving catch Wednesday, has had the worst offensive year of his life. The list just keeps going on.

So much scar tissue must be grown into the tough hide of a champion or even a serious contender for such a distinction. Reputation is endangered daily and in public. Before he talked to the press, Soriano, in a gray suit with white shirt and black tie, asked to be allowed a minute to find a mirror. “Let me get my tie up, please,” he said, just asking for a bit of dignity to remain.

“When you’re a young team, you take your lumps before you build that team that everybody wants to see,” Clippard said. “That’s what makes it so great when you get there. It’s got to be the most fulfilling thing in the world — to go through what we’ve gone through and finally get there.”

On some days, like this one, the hard trip seems even longer than usual.

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