Roger Federer still has two or three more years left in him at the highest level, according to Gustavo Kuerten.

The 20-time major winner returned to the French Open for the first time since 2015 this year and made it all the way to the semi-finals, where he was resoundingly beaten 6-3 6-4 6-2 by the irrepressible Rafael Nadal.

Nadal is now unbeaten in six meetings with Federer at Roland Garros, with the Swiss having won just two matches on the red dirt against the 'King of Clay'.

The 37-year-old has pared back his schedule since a series of injury problems in 2016, but three-time French Open winner Kuerten does not anticipate him retiring soon.

Asked how long he expects Federer to continue playing, Kuerten joked to Omnisport: "I guess two to 20 more years!

"I guess it's his choice, you know. I understand he would be able to stay for a while. Two, three more years, another Olympics try to [get a] flavour [of] the gold on singles.

"It's his call, more than ever. We already applaud him and being so fortunate to watch all of his glamorous career.

"Federer for me is much more than tennis and sports. It's kind of human patrimony that we are receiving over these last 20 years."