Fritz outguns eighth seed Ruud to reach US Open quarters
Ruud was sharp at the outset, breaking for a 5-3 lead before grabbing the first set with a love hold.
But the American began to make inroads against Ruud's serve in the second and finally converted a break when the Norwegian, who had been using a towel to wipe up his own sweat from the court on a humid day in New York, double-faulted on set point to level the match.
Ruud changed into dry clothes and shoes before the third but never regained his form in the match.
He produced a horrendous service game that ended with him dumping a backhand into the net to fall 2-0 behind in the third and Fritz, seeded 12th, captured the set with an ace.
Fritz kept his foot on the gas in the fourth, hammering his 24th ace on match point to set up a quarter-final meeting with either fellow American Brandon Nakashima or German fourth seed Alexander Zverev.
