Andy Roddick reached the quarterfinals at the Miami masters tournament by beating Benjamin Becker 7-6 (4), 6-3.

Seeded sixth, Roddick improved to 23-4 this year, and he leads the men's tour in wins. He's seeking his first Miami title since 2004 and hoping to spoil a potential showdown Sunday between Roger Federer and Rafael Nadal.

Three-time champion Venus Williams became the first women's semifinalist by beating No. 6 seed Agnieszka Radwanska 6-3, 6-1.

Roddick rallied on the strength of his dominating serve. He dug out of a 1-4, love-40 hole in the first set and won 34 of his final 39 service points, including all six in the tiebreaker.

A big serve helps, too. When Roddick found himself in another hole serving at 4-5, love-30, he responded with three service winners and an ace.

Roddick made another one on match point, closing out the victory with his seventh ace of the match and his 343rd of the year, second-most on the tour.

Roddick has been broken only once through three matches and next plays No. 33 seed Nicolas Almagro, who eliminated No. 27 Thomaz Bellucci 6-4, 3-6, 7-6 (3).

Top-ranked Serena has been sidelined by a knee injury since winning the Australian Open in January. In her absence, Venus has become the woman to beat as she bids for her fourth Miami title and her first since 2001.

The oldest women's quarterfinalist at 29, Venus is the hottest player on the WTA Tour. She has won 14 matches in a row, and two more would give her three consecutive tournament titles for the first time since 2002.

In the men's fourth round, Mardy Fish retired with a sciatic nerve injury trailing Mikhail Youzhny 6-1, 1-0. The injury occurred when Fish took a tumble in the first set, causing discomfort from his back to his calf.

No. 5 Robin Soderling beat No. 9 Fernando Gonzalez 6-0, 6-7 (3), 6-2, and No. 8 Jo-Wilfried Tsonga swept No. 12 Juan Carlos Ferrero 6-2, 6-2.