Heat break much more hectic than it seems

Don’t be late. The USTA invoked its new extreme heat policy for a second straight day and finally revealed its harsh penalty for taking too much advantage of the generous new rule.

With temperatures approaching 100 degrees, the USTA allowed a 10minute locker-room break after certain sets. For the women it’s after the second set of their best-of-three. For the men, it’s after the third set.

According to a USTA official, the 10-minute break is ironclad — with a point deducted for every 25 seconds a player is late following an initial warning.

So far, nobody has violated the 10-minute rule, though it’s unclear exactly when the umpire starts his clock. Ironically, 15th-seeded Stefanos Tsitsipas, lost in the second round in four sets to Danill Medvedev and mistakenly didn’t take the 10-minute off-court break.

“I had so many things I had to do so I actually forgot I had [a break],’’ Tsitsipas said. “After a couple of minutes I realized he was not on the court. It was only six minutes more left. I decided to stay and think, make a plan of my tactics on that side.’’

As far as another key rule of the heat policy, Andy Murray said after his loss that he informed the USTA that Fernando Verdasco chatted with his coach in the locker room during the 10-minute break — a violation.

“We were clear you don’t speak to your coaches,’’ Murray said. “They obviously weren’t in there for long, but you got to do better than that.”

The unseeded Murray, rehabbing from hip surgery, predicted he wouldn’t know how he’d feel after a four-set first-round win. And the answer was not good enough as the crafty veteran Verdasco took him out in a 3-hour, 23-minute, four-setter 7-5, 2-6, 6-4, 6-4.

➤ Long after almost all of the crowds had left and every other match had finished, Karolina

Muchova turned off the lights with one of the top upsets so far of the U.S. Open.

The 202nd ranked player in the world stunned No. 12-seed and former world No. 1 Gabrine Mu

guruza 3-6, 6-4, 6-2 in the second round late Wednesday night at Armstrong Stadium.