Roger Federer closed out this year by reaching the semi-finals of the ATP World Tour Finals, suffering a two-set defeat to Stefanos Tsitsipas.
And the Swiss sensation named the Greek youngster as one of the players he is worried about next season.
Tsitsipas enjoyed a successful breakout year, during which he reached the semi-finals of the Australian Open and won the ATP World Tour Finals in London.
The Greek, 21, beat Dominic Thiem at the O2 Arena in a three-set thriller earlier this month.
Straight afterwards, he travelled to Mexico City for an exhibition against Federer – one which drew in 45,000 fans.
Federer came out on top in that match, winning 3-6, 6-4, 6-2.
But clearly, the Swiss star has seen the youngster’s talent up close.
Speaking to TMZ on Monday, he named Tsitsipas as one of the two players he fears ahead of next season.
Federer also pointed out his worry over Alexander Zverev’s talent, saying he will be one of the ones who will make it difficult next season.
“There’s a few guys right now,” he said of the young players challenging the hierarchy next year.
“They’re going to make life difficult for us next year.
“I think Zverev, Tsitsipas and a few others are gonna make it hard.”
Zverev also had a good year, reaching the quarter-finals of the French Open and the semi-finals of the World Tour Finals.
He struggled slightly during the start of the year, after dropping out of the Australian Open in the fourth round.
He fell out of the world top five for the first time in two years after losing in the fourth round at the US Open later in the summer.
However, Federer is still clearly a fan, and believes he is in for a big 2020.
