This was his first match in the tournament since appearing last three years ago. "I feel that I'm playing good here". I should have played him here a year ago, but I was sick.
After been given a first-round bye, Federer took to the Stadium Court at Crandon Park for the first time since losing to Kei Nishikori in the quarter-final in 2014 having missed the last two years in Florida.
"I would love to play against him", Federer said of the 2009 U.S. Open champion before the match against Haase had occured. He slammed a volley that almost knocked Tiafoe over (not intentionally), a reminder to Tiafoe that polite as he might be, Federer is intensely competitive.
Tiafoe provided a good competitive workout for the 35-year-old Swiss maestro in his first match since he won the BNP Paribas Open at Indian Wells on Sunday.
Taking the ball early, the No. 4 seed should be able to dictate most of the baseline rallies and keep the ball just enough to Del Potro's vulnerable backhand in order to prevail.
Tiafoe, 19, is highly rated, but the American struggled to get anything going against the Federer serve, winning just 11 return points. You name it-we've had some really good ones. It should feed a player like him with a lot of energy moving forward hopefully.
"I would love to play against [del Potro]", Federer said, speaking before knowing who his next opponent would be.
Despite the gulf in experience between the players, Tiafoe underlined his status as one of the brightest talents in the game with a spirited display full of huge potential and winners off both wings.
In other men's action, Spain's Roberto Bautista Agut defeated Kazakhstan's Mikhail Kukushkin 6-3, 7-6 (7-3), while Switzerland's Stan Wawrinka defeated Argentina's Horacio Zeballos 6-3, 6-4.
Tiafoe broke early in the second set, but fourth seed Federer broke straight back with a sizzling backhand victor and another break was all he needed to clinch his 1094th career victory at tour level.
But 17th seed Anastasia Pavlyuchenkova was sent packing, beaten 4-6 6-0 6-3 by American Bethanie Mattek-Sands.