NEW YORK - Top-ranked Roger Federer continued his dynamic U.S. Open form in near-tropical conditions on Saturday while fourth seed Serena Williams braved the steaming heat to avenge a shock defeat she suffered in January.
With a potential semi-final showdown with Federer looming, Andy Murray remained in the hunt for his first grand slam crown by defeating Spain's Feliciano Lopez to reach the fourth round.
Women's second seed Agnieszka Radwanska set up a fourth-round tussle with Italy's Roberta Vinci by stopping Jelena Jankovic 6-3 7-5 at a steamy Arthur Ashe Stadium.
"With the hot conditions you really have to fight yourself more than your opponent," said Pole Radwanska, a sentiment echoed by several players.
Federer cruised past Fernando Verdasco 6-3 6-4 6-4 in two hours and two minutes, blasting seven aces and 30 winners against the 25th-seeded Spaniard.
The Swiss master, however, deviated from his normal baseline game and rushed the net 27 times, a tactic that earned him 26 points.
"I had no clue my stats were that good," he said. "Fernando did have some good chances for good passing shots. Looking back, I don't remember missing too many volleys and overheads.
"Probably half the time I didn't have to volley because it was hard to hit a good pass. It was windy. Usually when I do come in, it's probably on one I can be very offensive on."
Federer has not lost a set at the U.S. Open this year, as he moves closer to a sixth title at the National Tennis Center. Next up is either American Mardy Fish or Frenchman Gilles Simon for a place in the quarter-finals.
Verdasco, 28, had 35 unforced errors and 10 double faults as he lost to Federer for the fifth time in as many meetings.
Like Federer, Williams has not lost a set but needed a break of serve in the final game of the opening set to grab the momentum as she ousted Russian Ekaterina Makarova 6-4 6-0.
Makarova buckled under the pressure of her first-set letdown and was blown away in the second in just 32 minutes.
The Russian knocked out Williams in the fourth round of this year's Australian Open and the American said she was motivated to turn the tables at the year's final grand slam tournament.
The 30-year-old Williams, a three-times U.S. Open winner and 14-times grand slam champion, said it was painful to watch a video of her defeat by Makarova.
"Knowing that I lost (I thought it) could definitely happen again," said the Wimbledon and London Olympic champion. "I did not want that to happen.
"Whether I learned something from that match, I don't know. I really hate watching matches that I lose unless I'm punishing myself. I didn't punish myself."
Williams punished Makarova on Saturday, enjoying a 31-10 advantage in winners and claiming all eight of her service games.
Murray, who won Olympic gold last month, recovered from a mid-match lapse to defeat Lopez 7-6 7-6 4-6 7-6 in three hours and 53 minutes.
The Briton was leading 4-2 in the third set before Lopez fought back to send the match into a tense fourth set.
"The last few sets were tough," said Murray. "I just played a little bit better at the end of the tiebreaks, a little bit more solid than him, and that was the difference."
Murray said the oppressive heat made the match "mentally and physically challenging".
"I actually felt better towards the end of the match than I did maybe halfway through it," he said. "It was probably down to a combination of things, having not played that much in these conditions. It's just taking a while to get used to it.
"I usually have three weeks in Miami before the U.S. Open but I couldn't this year because of the Olympics. It was a nice problem to have though."
A sombre Lopez said Murray deserved to win the match.
"I was two sets to love down and I was still was believing that I could make it, even a break down in the third," he said. "It was a tough, tough match. Long rallies. It was hot.
"Andy's making you always play one extra ball. It's not like I should have won but I could have won."
Third seed Murray next plays 15th-seeded Canadian Milos Raonic, who beat American James Blake 6-3 6-0 7-6. (Editing by Tony Jimenez and Nick Mulvenney)