Sinner was beaten by Novak Djokovic in a thrilling five-set semi-final at the 2026 Australian Open that lasted four hours and nine minutes.
The Italian has won just six of the 16 five-set matches he has played in his career (37.5%), and he has a 2-10 record in five-setters against top 50-ranked opponents.
The four-time Grand Slam champion has lost all eight of the longest matches he has played in his career, and he has not won a match that lasted longer than three hours and 48 minutes.
The 24-year-old’s last victory in a five-set match was against Daniil Medvedev in the final of the 2024 Australian Open.
Volandri, who has captained Sinner in the Davis Cup, weighed in on Sinner’s poor record in Grand Slam matches that go the distance.
“You don’t yet know yourself well enough to be able to say, ‘I know what to do because I’ve been there before and I know my body well’,” the former world No 25 told SuperTennis TV (translated from Italian).
“Jannik has improved a lot in recent months, too. He still doesn’t have a high enough number of matches to be able to say, ‘Now I’ll get there and manage this situation because I know I have margin.
“He knows when to go into a sort of economy mode, and he demonstrated it in the last indoor tournaments of last season, where his energy level was very low.
“But in my opinion, he still doesn’t know himself very well when it comes to the fourth or fifth set, so he doesn’t know how to handle himself.”
Former Italian ATP Tour player Paolo Lorenzi expressed his confidence that Sinner will overcome his five-set struggles.
“That’s normal, because in his last eight five-set matches, he didn’t lose because he was weaker, but perhaps because he doesn’t yet have that experience,” said the former world No 33.
“However, there’s optimism; with time, he’ll become a devastating player in the fifth set as well.”
