By Steve Keating
NEW YORK (Reuters) - Stan Wawrinka fought off punishing heat and a youthful challenge from French qualifier Ugo Humbert to earn a 7-6 (5) 4-6 6-3 7-5 win on Wednesday and a spot in the U.S. Open third round.
With temperatures at the Billie Jean King National Tennis Center once again nudging towards 100 degrees Fahrenheit (38°C), Wawrinka and Humbert battled for nearly three hours and 30 minutes in the shadeless oven that is the Grandstand Stadium court.
Wawrinka, who won the U.S. Open in 2016 but was unable to defend his title last year after undergoing knee surgery, had his fitness put to the test by the 20-year-old Humbert playing in his first Tour level event.
Humbert let the three-times grand slam-winning Swiss know he was in for a long and sweaty afternoon after the first set went to a tiebreak and he levelled the match by taking the second.
But the barrel-chested Wawrinka's lived up to reputation as a battler and grimly hung on to take the next two sets.
Wawrinka, who upset eighth seed Grigor Dimitrov in the opening round, now faces 25th seed Milos Raonic after the big-hitting Canadian blasted past Frenchman Gilles Simon 6-3 6-4 6-4.
(Editing by Ed Osmond)