Federer made his comments while he was in South America during the week for two exhibition matches against del Potro in Buenos Aires.
“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 is 13-4 in his career against del Potro, but one of the losses came in the finals of the 2009 US Open to give the Argentine his only grand slam. In that tournament, Del Potro became the first player to ever beat Rafael Nadal and Roger Federer in the same grand slam event. Del Potro has beaten Federer the last two times they’ve met — including at the finals of the Swiss Indoors — though Federer beat the Argentine at the Olympics.
The truth is del Potro seemed headed to the top of the world rankings until a wrist injury derailed his career in 2010. After missing nearly the entire season, del Potro plummeted in the world rankings. He had a slow 2011 season as he came back, but he began looking much better in 2012. He reached the quarterfinals of three of the four grand slams.
Few doubt that del Potro has the game to win majors and to possibly achieve the No. 1 ranking the way Federer believes. We just saw Andy Murray have a major breakthrough in 2012, so we know it’s possible for something like that to happen.