Twenty-two-time grand slam champion Rafael Nadal was upset.
Frances Tiafoe had ended Rafael Nadal's 22-match Grand Slam-winning streak on Monday and reached the US Open quarterfinals for the first time.
"I felt like the world stopped," Tiafoe said. "I couldn't hear anything for a minute."
In a match that lasted more than 3 hours and 30 minutes, the Maryland native defeated Nadal 6-4, 4-6, 6-4, 6-3.
Earlier in the tournament, Tiafoe said he was happy to be going mostly unnoticed.
Nadal, 36, recorded his first loss in a grand slam event this year and is now 22-1 this season.
"The difference is easy," Nadal said afterward. "I played a bad match and he played a good match. At the end that's it, no?"
Nadal said he needs to "fix things" and when he feels mentally ready to compete again