Seventeen-time Grand Slam champion Roger Federer believes Argentine Juan Martin del Potro has the potential to become world number one.

The Swiss veteran was beaten 3-6 6-3 6-4 by del Potro in the first of two exhibition matches during his post-season tour of South America.

Del Potro burst onto the scene in 2009 when he stunningly beat Federer in a gruelling five-set encounter in the US Open Final, a victory which represents his only Grand Slam title to date.

The 24-year-old has been hindered by injuries in the past few seasons but with the Argentine now back in the top 10 Federer believes del Potro will rise even further up the rankings as his career progresses.

"He is already among the best, now he just has to train hard and stay on the same path," Federer said.

"He was No. 4, he's now 7, but he could be No.1. Sometimes the difference is in the small details."

Federer also admitted he has entertained the thought of a career in coaching when he draws the curtain on his playing days but insisted he is a long way from making a firm decision.

"(I) could be a coach, but I do not know. I'll see what the situation with my daughters and wife is. I still like to travel, but also enjoy being at home. I'm so happy," he said.