Andy Murray recovered from his win in the early hours of Thursday to beat Spanish wildcard Marcel Granollers and reach the Madrid Masters last eight.
The British number one, 27, recorded a 6-2 6-0 victory in his second match of the day, having started the tie against Philipp Kohlschreiber after midnight.
A "very tired" Murray said he had to "bluff" Granollers.
"If they want to see top players playing the best tennis, don't play at three o'clock in the morning," he said.
"I tried to pump myself as much as possible for this match and bluff him to show I was feeling OK.