The Croatian, whose last semi-final appearance at a major was at the 2018 Australian Open when he reached the final, encountered stiff resistance from Rublev but his 33 aces made the difference.
The 2014 US Open champion next faces either teenage sensation Holger Rune of Denmark or Norwegian eighth seed Casper Ruud. Rublev played with accuracy in the first set, which he won with a break of serve in the 11th game having not faced a single break point. But Rublev found some new energy in the fourth, playing more aggressively and with more power to break for 5-3 and hold to send the match into a decider.