Roger Federer says that Rafael Nadal and Novak Djokovic have done 'extraordinary' things in tennis.
Federer has seen his two main rivals equal his two biggest records in the last few months.
In October, Rafael Nadal drew level with him on 20 career Grand Slam titles when he won yet another Roland Garros title in Paris.
This week, Novak Djokovic equalled his total of 310 weeks at world number one, and the Serbian will surpass that figure on Monday.
It has made for what has become a lively debate on who the greatest of all time is, and Federer is proud to have a place in it.
"I think it's a great debate to have," Federer said in Doha.
"What Novak and Rafa have done lately is extraordinary, they're not 25-years-old either, but they seem at the peak.
"For them I am maybe the measuring stick, like Pete [Sampras] was for me."
Federer also had special mention for Nadal, whom he has been able to develop a friendship with in recent years.
"I saw him grow, right in front of my eyes. He’s one of the guys from tennis - players - that I could call up and, if I told him something, it would be a secret between the two of us.
"And I appreciate that we were able to build a relationship like that.”
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