Cape Town - The normally even-tempered Roger Federer was feeling a little bit aggrieved after receiving a code violation during his defeat to Kei Nishikori at the ATP Finals on Sunday.
Federer's quest for a seventh ATP Finals crown and 100th ATP title got off to a less than stellar start, as an error-strewn performance from the Swiss great resulted in a 7-6 (7/4) 6-3 victory for Nishikori.
To make matters worse, Federer was also handed a warning by Steiner for hitting a ball into the crowd.
Early in the second set, Federer was angered by a challenge, and made his feelings known.
When asked if he was unhappy with the umpire, Federer said: "I was, just because I thought what was his argument, why the warning?
"But nothing more than that. He thought I was angry. I wasn't. Now I'm angry because I lost, but I wasn't, so... "He knows me very well apparently, or he thought so."
Federer's form has been pretty good heading into the ATP Finals, having made it to the semi-finals in Paris where he lost to world No 1 Novak Djokovic, but there have also been a few disappointing results mixed in.
Still, he was at a loss to explain his poor performance against Nishikori.
"I've been feeling fine," he said. "It's just that practice has been a bit all over the place. Practised in Queen's, practised on the outside courts here, then centre as well.
"So it's not always exactly the same conditions. Overall I thought I'm hitting the ball okay. The warm-up was totally fine."
Federer was left to lament giving away the early break he'd earned in the second set almost immediately, and he identified that as the turning point in the match.
"Unfortunately I couldn't keep the lead that I got early. That was important at the end," he said.
"That was the key of the match. That 10-minute swing at the end of the first throughout maybe one-all in the second."