British teenager Jack Draper collapsed with apparent heat exhaustion during his first-round match against Mikhail Kukushkin at the Miami Open on Thursday.
The 19-year-old, who was making his ATP Tour debut after being awarded a wild card to the Masters 1000 event, was forced to retire with humidity hitting 79 per cent.
Draper is one of Britain's brightest prospects and he showed more than enough in the 79 minutes it took for Kukushkin to win the opening set 7-5 to indicate he can play at this level consistently in the future.
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But physically Draper clearly has work to do. He began to look increasingly troubled by the Florida heat and humidity and called the doctor trailing 6-5.
After having his heart-rate checked and blood pressure taken, Draper resumed, but down set point he fell to the floor.
He was swiftly attended to by medics and was sitting up with an ice pack on his neck when the umpire called the match for Kukushkin.
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Johanna Konta secured just her second victory of the season, beating Magda Linette 6-4 7-5 in the second round.
The British No 1, who won the biggest title of her career in Miami four years ago, suffered a setback when she sustained an abdominal injury during her first-round match at the Australian Open.
She had played just one match since but battled her way past Pole Linette, recovering from losing a break in the second set by winning the last three games
Konta said: "I'm really happy to come through that. It was a tough match against a tough opponent in tough conditions. It was hot, it was windy, so it was a lot of things out there to contend with and I was just really pleased that I was able to compete well and find a way to come through."
Konta also revealed she will not be part of Britain's Billie Jean King Cup - formerly Fed Cup - team when they take on Mexico in a World Group play-off in London next month.
She wants to give her troublesome knee time to adjust with the clay-court season coming up.
Liam Broady pushed Serbia's Miomir Kecmanovic but ran out of gas down the stretch as he went down 7-5 6-7 (5-7) 6-1.
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