The normally cool Swiss picked up a rare code violation for ball abuse in the 12th game after Nishikori produced a staggering backhand victor down the line.
I thought what was his argument, why the warning?
"But nothing more than that".
"But there was always a part of me that believed I could make it back and I never thought it was impossible".
"I wasn't. Now I'm angry because I lost, but ..."
And once Federer was out of contention in the same tournament and Nadal had formally withdrawn from the World Tour Finals, Djokovic was assured of the year-end No1 for a fifth time. "I think maybe we both had a bit of nerves", Federer added.
"It's going to be a lot of fun but also a situation where I don't have much to lose".
Both players raised their level as 10 consecutive points, which included three match points for Anderson and two set points for Thiem, went with serve.
By the time he hit the clay of Rome, he had turned a corner, and when it came to the grass season, everything began to fall into place: finals at Queen's, title at Wimbledon, the title at the Cincinnati Masters-ticking off another first, the complete set of nine Masters titles-and then the US Open and Shanghai Masters.
"Unfortunately I couldn't keep the lead that I got early (in the second set),"Federer said". That was important at the end.
Anderson, the first South African to qualify for the tournament since Wayne Ferreira 23 years ago, did not make his first grand slam quarter-final until 2015 and has now reached two finals in as many seasons.
But Fleming was left baffled by Federer's display. "It's just that the clay has been less".
But it is hard to see anybody other than Federer or Djokovic prevailing. I think out of the taller guys, he's playing outstanding from the baseline. "I think I've had that pressure, not going out early, most of my career". Since 2011 I have not won the World Tour Finals but I have done well'.
"I'm just here to play my best tennis and do things on my side, if I can do that then I give my self the best chance".