13th seed Fritz mounted a stirring comeback from two sets down to dump big-serving Zverev out of the tournament, winning 4-6, 6-7 (4/7), 6-4, 7-6 (7/3), 6-3.

Confronted with Zverev's relentless serve, the American looked to be heading home but engineered a crucial break in the third set -- the first time the German had been broken in the entire tournament -- changing the momentum of the match.

"It was amazing to do that on Centre Court, two sets down in front of this crowd. It's a dream," said the American, who will face Italian 25th seed Lorenzo Musetti in the last eight.

"The thing was I still felt I was playing really well for being down two sets. I was just thinking it sucked to be playing this well and to lose in straights."

Zverev, wearing a support on his left knee, said he was "on one leg today" as a result of an injury he picked up in his third-round win against Cameron Norrie.

"It is nothing that I need surgery on," he added. "It is nothing that doesn't heal by itself. It just needs time."

The 27-year-old, who was runner-up at the French Open last month, played down fears he would not be able to defend his Olympic title at the upcoming Paris Games.