Nineteen-year-old tennis star Nicola Kuhn shocked fans during this year's Miami Open, after collapsing to the court in agony midway through his first-round match. Facing off-against German opponent Mischa Zverev, Kuhn came into the tournament with high expectations - clocking the rankings as the world's 255th best-ranked player.After storming to a 6-2 win in the first set, and a 5-2 lead in the second, these expectations certainly seemed to be well-based, but the Austrian-born Spaniard's night was soon to take an unexpected twist. After failing to convert an extraordinary eight match points, Zverev forced the match into its third set, and both players visibly tired after their physical exertions started to take their toll.During a battling rally in the heat and humidity, Kuhn chased down a short ball from his opponent, when he suddenly collapsed to the court - flat on his face - in front of the on-watching shocked crowds. 

After remaining face-down for almost 20 seconds, writhing in agony from his still yet-unknown injury, Kuhn was finally aided by his trainer, who helped roll the player over, and gave him a drink of water. 

Despite initial fears, the injury was later confirmed to be a particularly severe case of full-body cramp, which, despite the clear frustration and anger on the face of Kuhn, unfortunately forced the talented teenager into an early retirement. 

Watch the frightening moment in the video below.

Speaking on Twitter after the game, Kuhn seemed in slightly better spirits, however, and thanked fans for the their support throughout the match.

"Left it all on the court. The birthday didn't go as I wished but I'm grateful for all the support I received today."

Kuhn, who only turned 19 on Wednesday, also received support from Denis Shapovalov and Felix Auger Aliassime, both of whom wished the youngster well.