Stefanos Tsitsipas battled past Karen Khachanov and into the Rotterdam semi-finals before admitting he worried he may not be able to compete.
Khachanov played some brilliant tennis on the day, rekindling memories of his form at the end of the 2018 season when he won the Paris Masters and looked set for a major breakthrough.
However, Tsitsipas was able to come back from being a break down in the deciding set to book a semi-final clash with Andrey Rublev.
"He was playing great tennis and I wasn’t sure if I would be able to compete," said Tsitsipas.
"I had an amazing 5-0 lead in the second set and that brought a lot of confidence into my game.
"We had great rallies and the quality of tennis was excellent. You need to stay as calm as possible in three-setters.
"I have won a lot in the past and with experience, it gives me an idea of how to play in these tight moments."
Tsitsipas' biggest problem may be his own success in Rotterdam, where he also reached the doubles quarterfinals alongside his brother Petros.
“Physically, I have played a lot of tennis so far and this is probably going to be the most difficult task to overcome."
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