Tiafoe vomits on court during five-set marathon win
The American was sick just behind the baseline and again on the edge of the court at a crunch moment at 5-6 in the fourth set against Frenchman Arthur Rinderknech.
He managed to continue and came through 7-6 (7/2), 6-3, 4-6, 6-7 (4/7), 6-3 in 4hr 8min.
"Honestly, when I threw up, I felt like, returning 5-6, I could be out of here in two minutes, out of here in five minutes," he said.
"I think if it was, you know, any other event, I probably would have let it go. But here, you got to lay it all on the line."
Tiafoe, a two-time US Open semi-finalist, was playing in the middle of the day in hot weather, but he laid the blame at being over-hydrated rather than the heat.
"I threw up all electrolytes and water. Wasn't like food in the tank was the issue. Neither was the heat, really," he said.
"Look, man, things happen. It's been funny all the things I've been getting tagged with since then."
Asked how his recovery had been after the match, he said: "Horrible. It's been terrible."
Tiafoe, the 17th seed, will next meet Hungary's Fabian Marozsan, who also battled through a five-setter.