Having required four hours and 13 minutes to seal the win, Del Potro is pleased with the triumph.
"I felt good because I won a big battle for the first round," Del Potro told reporters.
"Of course, he's a very tough opponent. He played so solid on the baseline. We played every time long rallies. I had to make three or four winners in the same point to win the point.
"But it was really close for me. I think I was lucky maybe in the fourth set when I come back after being a break down. But I'm okay. I feel good with my level. My forehand was good. My serve improved since the last tournament. That's important."
Del Potro won the Grand Slam back in 2009.