New York: Britain’s Johanna Konta continued to enjoy her time in the sun and the U.S. Open spotlight as she stopped 18th seed Andrea Petkovic 7-6(2) 6-3 on Saturday to reach the fourth round of a grand slam for the first time.

It was the second upset in as many matches for the 24-year-old qualifier who toiled for three hours and 23 minutes in searing heat on Thursday 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 to Flushing Meadows 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.

‘It was definitely tough. Even if she’s not at her best she is one of the toughest competitors on the Tour,’ said Konta, 97 in the rankings. ‘I think you could tell she wasn’t going to give it to me those last three games.’

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

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 gruelling five set battle with countryman Lleyton Hewitt.