The Croat won 6-7(2) 6-3 6-4 against American John Isner at the O2 Arena. When he lost the opener on a tie-break, it looked like more misery for Cilic, but he responded in superb fashion, even if he needed some help from Isner’s mighty serve. Debutant Isner double-faulted to hand Cilic a decisive break in the eighth game of the second set and then did the same to gift Cilic a break at the start of the third.

Cilic wobbled briefly, handing the break back with a woeful game, but struck again with some bludgeoning groundstrokes and kept his composure to claim the win. “There was a little bit of luck involved,” said Cilic. Earlier, Novak Djokovic notched up his 834th Tour win in his storied career but the latest, a 6-4 6-1 rout of young German Alexander Zverev, will not be one for his scrapbook. 

There were few moments to test the 02 Arena’s crowd decibel-level monitor — a new gimmick this year — but despite not feeling well, Djokovic had too much guile for Zverev. His ability to play the percentages and churn out wins in third gear has been a key component in his rise to one of the all-time greats and that was all he needed.

Djokovic appeared to be suffering with a cold and grabbed a tissue from his pocket on occasions, but after some fierce resistance in the opening set, he ran away with the match. “A win is a win,” the world number one, bidding for a record-equalling sixth title at the ATP’s season-ender, told reporters.

“Somehow I managed to gather the strength when I needed it. It wasn’t a great quality tennis match to be honest.”