The Swiss, who started the season at No. 17 in the Emirates ATP Rankings, has soared back to No. 6. A decade ago he was the reigning two-time Miami Open champion.
“At 25 I was winning 90 per cent of my matches and eventually you’re on this train where you keep rolling and expect yourself to win a lot,” Federer said. “You play many more tournaments.
“It was an incredible experience being able to play at such a high level for so long and beating so many of the guys, winning so many finals in a row. It’s definitely different, especially this year, it’s very different to any other that I’ve ever experienced, as was last year with the injury, with the age, with the comeback.
“This is very special for me. I definitely see things different today than I ever have.”
“I was very happy for him last year,” Federer said of del Potro’s return. “I was supposed to play him here and then I pulled out, which was a pity for both of us.
“The comeback was great for him. He finished top 40, won the Davis Cup, it was a dream come true for him as far as I know. I’m focused on one round earlier though.”
Sixth seed Dominic Thiem is his projected quarter-final opponent and should he live up to his seeding he could set his third clash of the season with compatriot and top seed Stan Wawrinka in the semi-finals.
For now, the lone former champion in the field is relieved to back to full health. A stomach virus ruled him out ahead of his first-round clash with del Potro last year. This is the first time he will have played in Miami since 2014.
“I’m coming in with more confidence, which I prefer, of course,” Federer said. “I’m happy to be healthy this time around. Last year, I postponed the press conference three or four times because I wasn’t feeling well and then at the end it ended up not possible at all so it’s nice to be back here healthy.”