John McEnroe fears "something serious" will happen on court after players struggled with the blistering heat on the opening day of Wimbledon. Two-time finalist Ons Jabeur was the first to retire as she struggled to breathe late in the first set.
A fan needed medical treatment as Carlos Alcaraz's clash with Fabio Fognini was suspended for 15 minutes midway through the fifth set on Centre Court. And shortly afterwards, Elena-Gabriela Ruse was sick in a bin on court during her loss to American No.6 seed Madison Keys.
The temperature peaked at 34C at SW19 on Monday and McEnroe fears there could be more serious consequences it does not get any cooler.
"The heat affected him [Alcaraz] a lot more than I had anticipated, that can happen," McEnroe told the BBC. "It's a scary thing. I never cramped on a court, it's got to be torture. Who was it that was playing Madison Keys (Elena-Gabriela Ruse)? I don't recall her name but she was having all types of medical problems.
"It was really hard to watch in a way because you are worried that something serious is going to happen here. This is extremely difficult. I am sitting here with you now and I am like: 'Thank god it cooled off, Clare said bring John at 12 and I am like: No! I am not coming until it cools off'.

"But that affected him [Alcaraz] more than he even thought so come Wednesday he can cool off, back to business and then he will, I presume, get his act together."
One suggestion to keep the main showcourts cooler is to close the roofs. But Alcaraz is not a fan of playing matches indoors because of the sun.
He explained: "I think it shouldn't close the roof because we will play in outdoor tournament. So the roof is just because if we can't play in another way.
"I think battling the heat, the hot, I think is one of the things that we have to do. Probably the match can't be in a way, in another way, because of the hot. I think we have to deal with it in the best way possible.
"Obviously for the fan, and even here in London, they are not used to having this weather. Sitting five hours in the stand without moving, the sun hitting, I think could be really difficult to deal with for the spectators.
"But we are playing outdoor tournament, so I think that the roof shouldn't be closed because of it."
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