Retired tennis star Boris Becker recently joined the coaching team of Danish player Holger Rune, and the German stated it would be ludicrous to believe his ward would become the World No.1 or win a Grand Slam title overnight.

Rune has had a subpar second half of the season, and recently split with Patrick Mouratoglou, former coach of Serena Williams. However, rumors began circulating that Rune was working with Becker when the youngster posted a photo of himself training with the German legend.

In an interview with Eurosport on October 19, Becker acknowledged joining Rune's camp. The former World No.1 gave some insight into his thought's on Rune's ability, and stressed the 20-year old had some ways to go before winning his first Major or clinching the World No.1 position.

"It would be bulls**t to claim now that Holger will become No. 1 or win the French Open," said Becker. "My ambition is to find the best Holger Rune. To do that, the tournament schedule has to fit. If he plays every week, he will eventually get tired.

"That's why I have to have a big say in this, according to the motto: 'Here we have to insert a training week, here we have to regenerate, and maybe you go on holiday with your girlfriend for 10 days'. That is part of the planning, because in the end, I am jointly responsible for the success."