He hasn’t quite got his number yet, but Pete Sampras suspects it’s inevitable Rafael Nadal will match his grand slam tally and probably catch leader Roger Federer as well.

A frustrated Nadal remains stalled on 13 career major titles, one shy of Sampras and four adrift of Federer, after a back injury made it “impossible” for the world No.1 to beat Swiss underdog Stanislas Wawrinka in Sunday night’s Australian Open final at Melbourne Park.

It’s the fifth time injury has cruelled Nadal’s Australian Open hopes and once again left the Spaniard cursing his battered body for letting him down.

“The whole year you are working for a moment like this and the moment arrives and you feel that you are not able to play at your best,” said Nadal, who first felt something amiss during the warm-up before his 6-3 6-2 3-6 6-3 defeat.

“So it was not an easy situation for me to be on court like this, but I tried hard until the end.

“I’m obviously disappointed and very sad about what happened. But that’s life, that’s sport.”

Injury appears all that stands between Nadal and further greatness and his Australian Open history highlights the risk of his high impact game.

While he owns one Open title from 2009, he missed the 2006 Open with a foot injury, retired injured against Andy Murray in 2010, suffered a hamstring injury losing to David Ferrer in 2011 and missed last year’s tournament as he returned from knee tendinitis.

Despite his latest setback on Sunday, Nadal increased his lead atop the world rankings over Novak Djokovic and, his body willing, will head to the French Open in May as a huge favourite to claim a ninth crown in Paris, and that 14th major.

“He’s in his prime now. Everything is just second nature,” said Sampras after watching the baseline warrior in action courtside for the first time in Melbourne.

“Rafa’s speed, he’s such a great athlete. He’s the best one out there. Some of the passing shots … it’s just a constant pressure from Rafa.”

Sampras says Nadal and Djokovic have taken the sport to a new level since surpassing long-time standard bearer Federer.

“Roger’s still there and he’s close, but I just think that Rafa’s in his prime now,” he said.

“If you think what Roger was doing when he was 28, he was dominating.”

Sampras believes it’s unlikely Federer will ever beat Nadal again over five sets and says the only way the Swiss can challenge his Spanish nemesis is through relentless attack, like Wawrinka on Sunday night.

“I would come in (to the net), especially when I see him returning from so far back in the court,” the American said.

“I would just move forward. The last thing you want to do is get into long rallies with Rafa. I mean, Roger’s good at it. But you can’t maintain it.

“To me, I would be aggressive. I would take advantage of his second serve, chip charge. Even if I was missing, you still have to. These guys want you to stay back try to rally and it’s a losing battle.

“So I would come in on both serves, get him on the backhand and just close (in).”