Nadal to remain number 1 as he reaches Aus Open quarters

Spain's Rafael Nadal ensured that he will remain world number one after he went past Argentina's Diego Schwartzman in four sets to reach the Australian Open's quarterfinal on Sunday. The other two players comprising tennis' 'Big Four' competing in the Australian Open, Novak Djokovic and Roger Federer, have reached the pre-quarters with their respective straight-set wins.