Italian Fabio Fognini reached his first Masters event semi-final after completing a surprise 7-6 (7-0) 6-2 win over seventh seed Richard Gasquet.
World number one Djokovic was not bothered by his sprained ankle.
The 32nd-ranked Fognini made his first significant breakthrough in a Masters Series event.
Fognini, who lives just across the border and said he felt "at home" in Monaco, produced a fine performance with his dropshots and deep spinning forehands troubling France's Gasquet.
The stands started to empty after he secured his victory and he will need his status as a fans' favourite when he faces Djokovic, who moved far better on the clay than he did in the first two rounds when he had to recover from a set down.
Last year's runner-up Djokovic, who picked up a ankle injury while on Davis Cup duty with Serbia less than two weeks ago, was pleased by his physical improvement.
"It's a great step forward for me," he said.
"I did not have the feeling that the ankle was bothering me, I was very solid. I elevated the level of my game in the past two matches, definitely," he added while a rainbow shone in the light rain falling over Centre Court.