MELBOURNE: Rafael Nadal Saturday said only a mental block was stopping Andy Murray from becoming the world's best player after he blew a golden chance to reach the Australian Open final.

Nadal, who will play Novak Djokovic in Sunday's title match, said Murray could be crowned world number one this year and was "unlucky" not to have won a grand slam.

But he highlighted a weak fourth set in Friday's epic, near five-hour clash with Djokovic, when Murray threw away a two-sets-to-one lead. The Scot fought back in a nail-biting fifth but he cracked when serving to stay in the match.

Spain's Nadal, a 10-time grand slam winner, said it was an opportunity missed for Murray, who is seeking to end Britain's 76-year wait for a major men's title.