Rafael Nadal praises the potential of Aussie teenager Bernard Tomic, as well as the heroic efforts of veteran Lleyton Hewitt.

"He understands the game," Nadal said of the 19-year-old Tomic. "His position on court is fantastic. He's young, and probably he's doing great mentally. He stays very relaxed with, positive face, even when the match is tough for him, I saw him always with calm and accepting everything really well. That's the right tactic to be a champion. Probably he's one of these players that have a very good chance to be there. For sure after, in terms of the game, he need to improve things. Need to keep improving things. But with 19 years old he is No. 30 of the world winning three very tough matches [at the Australian Open] against three players with very good level. The normal evolution is to saw him, I don't know if this year, in the Top 10, but probably this year, next year."

Nadal also had kind words for the 30-year-old Hewitt, the former No. 1 who has also reached the fourth round of the Australian Open.

"I admire him a lot," the Spaniard said. "I think he deserve all the respect of the people who love this sport and respect and admiration of everyone, because after having, I don't know how many, five surgeries, having the motivation to run, to fight every ball. Even if the body don't have the perfect answer, is something fantastic. I have a good relationship with [Milos] Raonic, his coach [Galo Blanco] is from Spain so I am close to him. I really get emotional when [Hewitt] finished. He goes to the floor. He was really showing out his emotions, so is something fantastic at this moment of his career after having fantastic career. He's one of the more charismatic players on tour. I always liked him, his spirit of competition. He is an example to follow for a lot people."