Marin Cilic, gangling and seemingly lost, tottered about the arena like a giraffe that has just been shot with a tranquillising dart, writes Hugh MacDonald.

The Barclays ATP World Tour finals in the O2 Arena were supposed to be a joyous end to a triumphal season. At 26, Cilic has spent almost two decades playing tennis. For 10 years he has been on the professional circuit, travelling from a ranking of 1463 to a career high of eight this season. He has won 13 tournaments, mostly in places such as Zagreb, St Petersburg, Umag, Chennai and New Haven.

And yet on September 8, 2014, he did something stunning, almost unimaginable in the era of the Big Four. He won a grand slam, the US Open. This week he has won six games of tennis in two matches. As he stumbled in the O2 Arena against Tomas Berdych, beaten, 6-3, 6-1, it was almost possible to feel sympathy for a multi-millionaire. At 6ft 6in, Cilic was out of his depth. His first-match loss to Novak Djokovic was brutal. Berdych was similarly ruthless. The Czech's verdict on his opponent post-match was blunt but its validity was unquestioned: "Let's put it this way. With the way he played, he would never win a US Open,"he said.

Cilic, of course, could not comfort himself with any reflection on two hammerings but he could look back to that day in September for some warmth. "Having won a US Open is going to make this season look amazing," he said.

Another 2014 grand slam winner had a humbling day on court. Stan Wawrinka, winner of the Australian Open, stormed off to a sensational start against Novak Djokovic, racing to a 2-0 lead. Playing with vim and audacity, Wawrinka seemed to have unnerved the world No.1. Djokovic then won 12 of the 13 games played subsequently in a performance that combined his extraordinary athleticism with a flawless execution of strokes.

The Swiss player, energetic and forceful at the beginning of the match, was reduced to a forlorn victim long before the end. There was a moment in the second set where he seemed to have outmanoeuvred Djokovic with a drop shot stranding the Serb so far behind the baseline he was barely on the same side of the Thames.

Djokovic, almost inevitably, not only reached the ball but deftly flicked it past Wawrinka. The Swiss player subsequently reached for his towel. Presumably, a white flag was not available.

Djokovic won 6-3, 6-0 in one hour and five minutes. Wawrinka was slammed grandly.