Having overcome a brutal wrist injury which kept him out of the majority of the 2014 circuit, the former world No.4 closed out Fognini 4-6 6-2 6-2 in an hour and 48 minutes.
Far better than his world ranking of 338 would indicate, Del Potro fell behind in the opening set when Fognini captured the first break at 4-3, going on to win the set as the Argentine struggled to hold his serve.
But the 26-year-old cruised to easy wins in the second and third sets to setup a quarterfinals showdown with Kazakhstan qualifier Mikhail Kukushkin, who also upset sixth seed Pablo Cuevas 7-5 7-5.
“I thought I played better (than yesterday’s first round match). I feel better on the court, especially in the end of the match. I serve well, I hit good forehands, and my backhands improved from yesterday to this match a little bit,” Del Potro said.
“I hit a lot of backhands from the baseline. I didn’t play too many slices in this match. I think I’m doing in a good way.
“I need to keep playing with these guys, hitting the ball as fast I can, and keep trying. My wrist is the same. It’s not getting worse, so I have confidence with that. Of course I’m very happy to beat my first top 20 player on the year.”
Still dealing with wrist pain even after an 11-month layoff, Del Potro required courtside treatment for the lingering injury, but fought through the discomfort.
“I’m not feeling like in the beginning of the last year for sure,” he said. “But for me playing two matches in this week is amazing. I didn’t expect to be in the quarterfinals in my first tournament. That will give me motivation for the future.”
Italian Simone Bolelli also advanced to the quarters after upsetting second seed David Goffin.
Photo: Matt King/Getty Images.