-- LONDON -- Novak Djokovic certainly seems wound up at the moment and he gave another clear indication of his mindset with an outburst at the chair umpire Thursday.
He became angered after chair umpire Fergus Murphy gave him a time violation for taking too long between points in the fourth game of his 6-1, 6-2 win against David Goffin at the Tour Finals. Milos Raonic later beat Dominic Thiem 7-6 (5), 6-3 in the evening session to join Djokovic in the semifinals.
But the world No. 2 was perplexed that he hadn't been given a soft warning first. "Can you explain why you didn't tell me before?" Djokovic said at the next changeover, explaining it was the first time he had gone over the allotted 25 seconds.
On the point in question, the Serb had taken 31 seconds to serve following a long rally that was ended by exquisite lobbed winner from Goffin, which had drawn a thumbs-up from Djokovic. "That's the rule," he was told bluntly by Murphy, though.
"That tells me that you have no clue about the game, you have no clue about the game," Djokovic shot back.
Murphy replied: "That's your view."
Djokovic continued to plead his case in what became a heated exchange. "He played an amazing point. I went to get my towel and you give me a warning right away," he said. "You think that's fair?"
"Yes, that's the way we enforce the rule and we've been doing that for two years," said the umpire.
Djokovic then stood up from his chair and gestured behind his chair to supervisor Tom Barnes, pointing one finger in the air and saying "one time" repeatedly.
He perhaps had a right to be annoyed. It was the first time in the match that Djokovic had strayed over the time limit between serves and a soft warning at the change of ends may have sufficed.
He sought out Barnes for a chat after the match to clarify the rules. "I just wanted to get his view on this," Djokovic told a post-match news conference.
"First of all, I accept and I know that I'm one of the players that takes the most time. There is no doubt. I'm not running away from that.
"Every time that I'm late, if I get a so-called soft warning or pre-warning, I'll accept it and I won't say a word. But I think it's fair, correct and respectful towards the player and to the game if you go over the first time, let's say, over the limit, that you at least get a heads up.
"That's all I'm asking for, to be honest. I'm not the only one who has that kind of mindset and perspective and opinion about this.
"I know that the rules are strict, you have to follow. But there should be a kind of a feel, a sense for the game. It was the fourth game of the match, after a long point, the first time I went over, a few seconds, he gives me a warning. I didn't think that was supported by the right facts. That's why I wanted to have a conversation and understand why it was as it was."
In the grand scheme of things, it did not matter at all. There was no fine for Djokovic, and he did not lose a point. What's more, his position as group winner and his place in the semifinals was already safe and this was essentially a dead rubber.
"No stress at all, why stress?" Djokovic said on court post-match. "We come here to play, to enjoy. This is one of the biggest tournaments in the world. I'm just having fun on the court."
But he was more forthright in his news conference about the pressure he is under.
"I mean, look, you know, we're all humans," he said. "Every single day we face some certain kind of challenges, mental challenges, on everyday basis, private, professional life, emotions, thoughts.
"It's normal, especially if you compete on the highest level in professional sport, that you have maybe more of that hype and emotions and adrenaline going through your body. It's very important always to kind of know how to filter all of that, how to channel it in a positive direction.
"Certainly there are stages of the year or of the day, moments when you feel worse, and you feel better. The important thing is to be conscious of it and just deal with it in a best possible way that works for you."
Djokovic will have known not to take Goffin lightly. The last time an alternate won a match at the Tour Finals, Djokovic was on the other side of the net, beaten 3-6, 7-5, 6-1 by countryman Janko Tipsarevic and eliminated from the tournament.
Tipsarevic had joked after that match that Djokovic might then cancel their planned post-season holiday together.
Here on Thursday, the 12-time Grand Slam winner managed to shake off the time violation incident to record a blowout victory. He took the first set in just 36 minutes and the second even quicker in 33 minutes.
"I was trying to put myself in the right state of mind regardless of who was at the net," said Djokovic, whose scheduled opponent Gael Monfils withdrew from the tournament with a rib injury Wednesday night.
"I felt the most comfortable today from all the three matches, and I felt I increased the quality of the tennis. It's not easy for him to come out, I think, to play. He didn't play his best."
The umpire incident aside, it was the perfect afternoon for Djokovic -- he didn't drop his serve, and will have conserved his energy for the weekend.
He now has a day off, while Andy Murray -- whom he is battling with to finish as year-end No. 1 -- faces a potential run of three matches in three days, should the Scot reach the final in what could be a straight shootout between the two to finish top of the rankings.
"I've played Andy many times this year," said Raonic, who is 6-0 against the Scot in 2016. "I haven't gotten the better of him. He's been playing well. He's been playing a lot of matches.
"I think the one thing that I might have is how much he has really on his shoulders right now, a lot of consecutive matches, and as well what he's playing for. I have to try to do my best to try to accentuate that as much as possible in my own favor so I can really get the most out of myself and hopefully be able to get on top of him for once this year."