Roger Federer and Andy Murray remained on course for a semifinal clash at the U.S. Open after they won in contrasting styles on Saturday.
Olympic champion Murray, still seeking his first Grand Slam title after four losses in finals, eked out a 7-6 (5), 7-6 (5), 4-6, 7-6 (4) victory over No. 30 Feliciano Lopez, who led in each of the three tiebreakers before faltering.
''Could have gone either way,'' Murray acknowledged. ''It was very hot and humid in the middle part of the match. I was struggling a bit with that.''
The biggest moment came a few minutes before the fourth-set tiebreaker when Murray saved a break point in a 24-stroke rally in which he drew Lopez into the net, then pushed him back and finally got him to net a backhand to push the game to deuce.
''He came to the net, there was a drop shot, I made a good volley cross court. Points like that can change the match.''
Murray won his 250th career match on hard court and improved to 104-65 in tiebreakers. His next match is against No. 15 Milos Raonic, a 6-3, 6-0, 7-6 (3) winner over American James Blake.
The man he beat for the gold at the Olympics, and lost to in the Wimbledon final, Federer, was barely bothered while dismissing No. 25 Fernando Verdasco 6-3, 6-4, 6-4.
Five of Federer's record 17 Grand Slam titles came at Flushing Meadows, and he's looking capable of adding to those numbers.
The Swiss did an unusual amount of damage at the net, closing out 26 of 27 points from the front court. Federer added that effort to the 32 points he won in 47 trips to the net two nights earlier in a second-round win over Bjorn Phau.
''I really tried to play offensive against ... Phau in my second match,'' Federer said. ''I did lose more points than I was hoping to. But I think that gave me the confidence to move forward today. And conditions helped that because it was quicker during the day.''
Federer next will take on No. 23 Mardy Fish, who overcame a whopping 75 unforced errors to outlast Gilles Simon of France 6-1, 5-7, 7-6 (5), 6-3 in a match that ended past 1 a.m. Sunday.
Other men's winners Saturday included No. 11 Nicolas Almagro, who ended the run of 19-year-old American Jack Sock 7-6 (3), 6-7 (4), 7-6 (2), 6-1; No. 12 Marin Cilic, who defeated No. 17 Kei Nishikori; and 50th-ranked Martin Klizan of Slovakia, who beat No. 32 Jeremy Chardy.
In women's action, Serena Williams overran Ekaterina Makarova 6-4, 6-0, winning the last eight games of the match.
The previous time these two women played each other, it wasn't close, either. The difference, surprisingly, was that Makarova won 6-2, 6-3 in the fourth round at the Australian Open.
That loss remains the only one for Williams in 22 Grand Slam matches against left-handers.
''Definitely was motivated. Knowing that I lost; could definitely happen again. Did not want that to happen,'' said Williams.
Williams has dropped only 12 games entering her fourth-round match against 82nd-round Andrea Hlavackova of Czech Republic. Hlavackova, the 2011 French Open doubles champion, bawled on court after her 5-7, 6-4, 6-4 win over 14th-seeded Maria Kirilenko.
The woman Williams beat in the Wimbledon final, second-seeded Agnieszka Radwanska, dealt with the stifling heat and former No. 1 Jelena Jankovic with equal aplomb during a 6-3, 7-5 victory.
''I was feeling like I was melting there,'' Radwanska said. ''I survived the match.''
Former No. 1 Ana Ivanovic ended 19-year-old American Sloane Stephens' run at the Open for the second consecutive year.
The 12th-seeded Ivanovic overcame 56 unforced errors, a deficit and a partisan crowd in Arthur Ashe Stadium to beat Stephens, 6-7 (4), 6-4, 6-2, in the third round Saturday night.
Ivanovic eliminated Stephens at the same stage at Flushing Meadows in 2011.
Since winning the 2008 French Open -- her third final in a stretch of five Grand Slam tournaments -- Ivanovic hasn't reached the quarterfinals even once. She'll get a chance to get to the last eight in New York after taking the last four games against Stephens, who at No. 44 is the youngest member of the top 50 in the WTA rankings.
Stephens hit 10 double-faults.
Among Saturday's other women's matches, sixth-seeded Angelique Kerber of Germany put in an eye-catching performance by cruising past Belarussian Olga Govortsova 6-1, 6-2.
