NEW YORK (Reuters) - Roger Federer produced another bright effort while Britain's Johanna Konta continued to enjoy her time in the sun and the U.S. Open spotlight on Saturday reaching the fourth round of a grand slam for the first time.
With five U.S. Open titles already in his trophy case, Federer has enjoyed many fortnights in New York and his efficient 6-3 6-4 6-4 third-round victory over Philipp Kohlschreiber will not count as his most memorable.
Konta, on the other hand, is unlikely to soon forget her 2015 visit to the National Tennis Center as the 24-year-old qualifier registered her second shock win in as many matches, stopping 18th seed Andrea Petkovic 7-6(2) 6-3.
Konta can also claim the title of Iron Lady of Flushing Meadows, after laboring for three hours and 23 minutes in Thursday's searing heat to dispatch eighth seeded Spaniard Garbine Muguruza in the longest U.S. Open women's match since the introduction of the tiebreak in 1970.
The sun returned on Saturday but again it was Konta's opponent feeling the heat, with Petkovic calling a medical timeout after going down a set and 3-0 in the second.
Trainers checked the German's blood pressure and wrapped her in ice packs and ice towels and she was able to continue digging into her reserves to offer up a brief fight back.
Up 5-1 and serving for the match, Konta could not put away Petkovic at first opportunity as the German broke and held serve.
But Konta would not let Petkovic off the hook a second time, serving out to clinch the upset.
"To be honest, I feel just as I did two weeks ago, I haven't exactly grown wings or anything," said Konta, ranked number 97. "I must say I'm happy with how I have been playing so far this week but my feet are firmly on the ground.
"I haven't cured cancer or anything."
Next up for Konta will be fifth seeded Czech Petra Kvitova, who had no problem with the heat or her opponent, the twice Wimbledon champion needing just 66 minutes to breeze past Slovakian Anna Karolina Schmiedlova 6-2 6-1.
One of just two players to beat world number one Serena Williams this season, Kvitova arrived at Flushing Meadows in good form having claimed her third title of the season at New Haven in the final tuneup for the U.S. Open.
It was another leisurely afternoon on Arthur Ashe Stadium court for Federer, who has yet to drop a set, though he lost his serve for the first time in the tournament as Kohlschreiber broke him twice in the 93-minute match.
Federer, who had sprinted through his first two matches with the loss of only nine games, next meets big-serving American John Isner.
The 13th-seeded American advanced when Czech Jiri Vesely retired with a neck injury when trailing 6-3 6-4.
"I think I won the big points today," said 17-times grand slam singles winner Federer. "I served well when I had to at the end."
Richard Gasquet also wasted little time in the sun, the 12th seeded Frenchman romping into the fourth round with a 6-4 6-3 6-1 win over a drained Australian Bernard Tomic, who was coming off a grueling five set battle with countryman Lleyton Hewitt.
There was some good news for Australian tennis fans as 2011 U.S. Open winner Samantha Stosur pushed into the fourth round beating 16th seed Sara Errani of Italy 7-5 2-6 6-1.
Editing by Andrew Both