WASHINGTON, March 30 (Xinhua) -- Rafael Nadal and Andy Murray both made the fourth round at the Miami ATP hard court tennis tournament on Monday.

    Number 1 Nadal fought off a challenge from 74th-ranked Portuguese Federico Gil to win a tight 7-5, 6-3 victory, while fourth seed Scot Murray downed Chile's Nicolas Massu 6-4, 6-4.

    "No opponent is easy, especially if you are not playing your best tennis," said Nadal. "Everything was more difficult today. I didn't play very well, and I had chances to lose the first set."

    Nadal's victory was his 23rd of the season against just two defeats as he strives for a third 2009 trophy.

    Joining in the last 16 in Miami were sixth seed Juan Del Potro as the Argentine beat Serb Janko Tipsarevic 6-4, 6-1, and Viktor Troicki who won over German Bjorn Phau 6-4, 6-3.