Djokovic, Federer show true grit

This is what makes a champion in tennis, one who can last through history. It wasn’t just that Novak Djokovic and Roger Federer were both about to lose, and made great escapes at the same time Tuesday in the quarterfinals of the French Open.

It was that they both won marathons that weren’t about endurance or fitness.

Frankly, as US tennis players once again just sit and watch the world’s best fight it out for a major championship, Federer and Djokovic won because of things that American tennis coaches don’t teach.

It was doubly enforced because you could see it in stereo.

Late in a five-set match that came after another five-set marathon in his previous match, wasn’t Djokovic exhausted?

“I guess at that stage,’’ he said in an on-court interview with the Tennis Channel, “you’re not really thinking if your body is tired or not.’’

Tennis might be the most cerebral sport. Djokovic, trying to become the first man in 43 years to win all four majors in a row, survived four match points and beat Frenchmen Jo-Wilfried Tsonga 6-1, 5-7, 5-7, 7-6 (8-6), 6-1. Federer, trying to add to his record 16 major championships, beat Juan Martin del Potro 3-6, 6-7 (7-4), 6-2, 6-0, 6-3.

And the truth is, neither Djokovic nor Federer has played great in this tournament.

Djokovic appears to be tired, and maybe pressured by the Grand Slam stuff. He has looked at times as if he doesn’t believe. Meanwhile, Federer is his usual cool, calm and collected, never getting upset, but also never really taking chances or going for winners. It looks as if he’s painting by numbers.

On top of that, neither one played as well as his opponent Tuesday. Add all of that up, and that’s what was so stunning about their escapes.

“The one that mentally, I think, pushes more, maybe in some points, and obviously gets a bit lucky, gets the win,’’ Djokovic said. “You know, that’s how it goes.’’

Federer was about to lose, but del Potro’s knee buckled. Federer, seeing a weakness, raised his own game.

But the Djokovic match was more interesting because Tsonga had it won, and then was blown out in the fifth set. How does that happen? It’s about the mentality of a champion.

Djokovic got aggressive on match points against him. It might be the best he ever plays, when he’s one stroke from losing. And when Djokovic got through that fourth set, Tsonga was done.

Djokovic said there was “no rational explanation’’ for why he plays well on match point against him. He has saved match points against Federer at the US Open two years in a row, including one with a crushing hit-as-hard-as-possible, go-for-broke return of serve winner.

Well, it was a mental beatdown from Djokovic Tuesday. In tennis, you cannot just coast to the end no matter how far you’re ahead. There is no clock running out, and no blowout lead can be safe. You have to keep winning all the way to the end.

It’s a little like baseball, in that no matter what’s happening, you still have to get the last out. In tennis, half the battle is getting to match point and the other half is winning it.

Tsonga couldn’t do it under Djokovic’s mental strength, and sat between games thinking, “This is a joke. How could I lose this match?’’

See, one little crack, one little mental opening left for Djokovic, and he stepped in.

Coaches everywhere are teaching kids about grips and strokes and footwork. And players keep getting bigger, more muscular, faster, too.

So they try to build champions with fitness and diet. That’s never going to be enough.

Maybe you just can’t teach that mental element, even if it is the most important one in the game. And these three guys — Djokovic, Federer and Rafael Nadal — just have something special.

But it stands out on a day like this that it has been years since the US has had anyone other than the Williams sisters who could win matches like the ones Djokovic and Federer won Tuesday. Meanwhile, coaches keep turning junior players into little clones, showing that there’s one way to swing a racket, one way to do anything.

This week, three men are reaching for all-time greatness at exactly the same time in the same place. And, of course, none of them is an American.

In addition to Djokovic going for the Grand Slam and Federer trying to add to his majors record, Nadal is trying to break Bjorn Borg’s record and win his seventh French Open.

Give a strong edge to Nadal, because he has the mental edge now over the other two. And that’s all that separates these three now.

For years, tennis fans thought they were going to have four greats, with Andy Murray. But Murray can’t win a major. At the French, after every point he loses, he reaches to his back, his knee, his ankle, as if pain has cost him.

Whatever. His problems aren’t even physical. Before last year, Djokovic used to be the same way, always looking for excuses instead of answers.

Now, Murray can’t stop thinking about his owies, and Djokovic says you don’t think about your body in big moments.

“I was fortunate to come back from four match points down,’’ Djokovic said. “I don’t know how I went through that.’’

It was all in his head.