Fifth-seeded Fritz played effortlessly at home the first two sets and seemed to be able to clear the quarterfinals without burning too much power and energy.
Then Chatjanov took himself by the scruff of the neck, won eight of nine games and reduced to 1–2 in sets.
It was during that time that the American's one foot started to malfunction. Fritz took a medical timeout and got his foot taped.
At a disadvantage with 0–2 in the fourth set, the American got his game in order again, went up to both 5–4 and 6–5 before he finally won the tiebreaker and the match.
World number two Carlos Alcaraz is on the other side of the net in the semifinals. The Spaniard sent out unseeded Briton Cam Norrie without any hassle in three straight sets – 6–2, 6–3, 6–3.
World number one Aryna Sabalenka lost the first set in her quarterfinal in the women's singles against German Laura Siegemund, but turned it around and won with 4–6, 6–2, 6–4.
After the first set, I thought it was time to book the flight tickets to leave this wonderful place, says Sabalenka to Max.
Siegemund, 37, has made a sensationally strong tournament and on the way to the quarterfinals beat, among others, Australian Open winner Madison Keys.
American Amanda Anisimova booked a spot in the semifinals against Sabalenka by beating Anastasia Pavlyuchenkova with 6–1, 7–6 (11–9).