ANDY Murray complained Fernando Verdasco might have flouted the rules during their 10-minute heat break on Wednesday in what became a second-round US Open loss for the 2012 champion.

Murray said after he was beaten by No. 31 seed Verdasco 7-5 2-6 6-4, 6-4 that the tournament did not do a good enough job of making clear exactly what is allowed and what isn’t during the time away from the court.

As Murray was bowing out No.1 seed and defending champion Rafael Nadal has powered into the third round with a straight-sets win over Vasek Pospisil. Nadal hit a barrage of winners and mixed in lobs and drop shots to confound the unseeded 28-year-old Pospisil, ranked 88th.

The Spaniard got an early break in the third set and raced ahead to a 6-3 6-4 6-2 victory.

He’ll face 27th-seed Karen Khachanov, 22, of Russia in the third round. The US Tennis Association decided on the fly to allow rest periods in men’s matches for the first time in US Open history as the temperature soared this week.

While the women’s rules already call for a break if the conditions are too extreme, there is no such provision for the men.

But on Tuesday, the USTA offered men a chance to rest after the third set if they want, then applied that rule on Wednesday, too.

“I went for a shower. He was having an ice bath,” Murray said about Verdasco. “When I came out of the shower ... one of the Spanish doubles players was in there chatting to him, and you’re not allowed to speak to your coach.”

The USTA said players were not allowed to consult coaches during the heat breaks.

Verdasco said that’s not what he was doing. He said he was chatting with another player and that player’s coach.

Stan Wawrinka fought off French qualifier Ugo Humbert to earn a 7-6 (7-5) 4-6 6-3 7-5 victory and a place in the third round.

The 33-year-old now faces 25th seed Milos Raonic after the big-hitting Canadian blasted past Frenchman Gilles Simon 6-3 6-4 6-4.

Russia’s unseeded Daniil Medvedev upset 15th seed Stefanos Tsitsipas 6-4 6-3 4-6 6-3.

Fifth-seed Kevin Anderson advanced with a 6-2 6-4 6-4 victory over France’s Jeremy Chardy.

John Isner reached the third round for the seventh consecutive year, beating 42nd-ranked Nicolas Jarry of Chile 6-7 (7-9) 6-4 3-6 7-6 (7-2) 6-4.