The answer will become clear when the defending champion plays his semi-final on Thursday (local time), against Novak Djokovic.
The Serb beat Felix Auger-Aliassime 7-6 (12-10) 3-6 6-3 6-7 (4-7) 7-6 (10-4) in a five hour, 15-minute epic that, to the relief of everyone involved, ended just six minutes before Wimbledon's 11pm curfew.
Assuming Djokovic is able to summon the required energy, and the 39-year-old's powers of recovery are remarkable, Sinner will surely need to up his game having struggled to put away Jan-Lennard Struff, the world No.74 on Tuesday (Wednesday AEST).
At 36, and in his 47th grand slam, Struff was the oldest man in the professional era to reach his first major quarter-final.
Sinner beat the German 7-5 ‌7-6 (7-4) 6-3, but made 26 unforced errors and had to save a set point in the second set.
"A very, very tough player to play against," said Sinner.
"He deserves everything he has done and achieved in his career. Great person off the court.
"In the beginning I felt like he started better than me, I was struggling a bit. I tried to get into the match, I was serving a bit better, tried to stay there mentally, and of course very happy to be back in the semi-finals here."
On another hot day in London, there was no sign of a return of Sinner's difficulty with the heat that caused his shock second-round exit in Paris last month.
"We worked a lot, especially after Paris, trying to understand what went wrong there. It was a huge test today. I felt really comfortable on the physical side today so a big step forward."
In the quarter-final suspended on Monday night by Wimbledon's curfew, second seed Alexander Zverev dropped the set in progress but still beat 13th-seeded Czech Jiri Lehecka.
Leading 6-4 7-5 3-3 overnight, Zverev failed to win another game in the third set. The fourth went with serve until the tiebreak, which the recent French Open winner took on his third match point, having double-faulted on his second.
Zverev, who will now play sixth-seed Taylor Fritz on Wednesday, said: "He (Lehecka) came out swinging, but I'm happy to be through in four sets and not having to play another today."
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