Rafael Nadal is still capable of winning more Grand Slam titles despite falling to Switzerland's Stanislas Wawrinka in the finals of the 2014 Australian Open Championship, according to tennis legend Pete Sampras.

Sampras, who collected 14 Grand Slam crowns during his heyday, believed Nadal is at the peak of his tennis career right now and likely bound to win more majors title in the next few years.

'He's in his prime now. Everything is just second nature,'' Sampras told reported via the Sydney Morning Herald. ''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.''

For the first time in his Australian Open campaign this season, Nadal was a far cry from his usual tenacious approach on the court as a crippling back injury limited his mobility in his championship match with Wawrinka.

Nadal could not hide his frustrations after absorbing a 6-3, 6-2, 3-6, 6-3 loss to Wawrinka, as he decided to have a moment of deep silence on his bench before accepting his runner-up plate.

''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 only dropped a set on his way to the finals.

The world's no.1 netter also received some jeers and boos from the crowd mainly because of his sluggish performance in the finals, but Wawrinka quickly came to his defense and insisted the crowd was unjustified for criticizing the ailing Spaniard.

Still On Top of the World

Despite his latest shortcoming at the Aussie Open, Nadal further padded his lead over rival Novak Djokovic in the latest ATP World Rankings. The Mallorcan Bull has already amassed 14,330 ATP points while the Serb fell to 10,620 following his stunning quarterfinal defeat to Wawrinka.

Nadal is scheduled to play in the upcoming hard court season, particularly in the ATP Indian Wells Open and the Miami Masters slated in the coming month. After that, he will prepare for the clay court season and the French Open championships, where he's the unanimous favorite to win his 9^th crown at Roland Garros.