Jack Draper -- a 19-year-old making his debut on the ATP Tour this week -- frighteningly collapsed on the court during a match at the Miami Open on Thursday ... but thankfully, he said afterward he's all right.
The scary scene all went down during Draper's match against Mikhail Kukushkin ... when Draper began to feel ill amid scorching Florida hot and humid weather.
At one point during the match, medics ran courtside tests on a visibly exhausted Draper ... but the young, budding tennis star elected to continue despite clearly being unwell.
A reminder that tennis can be brutal 😔
Not the way Britain's Jack Draper wanted to end his first match on Tour.