"When I had a great comeback saving six, seven set points, then I didn't manage to win that first set, of course you're frustrated", said Djokovic.
Djokovic established himself in the pantheon of all-time greats in June when his French Open triumph made him only the fifth man in the Open era to complete a clean sweep of the four Grand Slam tournaments.
The reporter had referred to this year's French Open at Roland Garros, where Djokovic narrowly avoided disqualification when his racquet slipped out of his hand and nearly swiped a line judge during the Serb's quarter-final win over Tomas Berdych. Novak Djokovic in joined in Group Ivan Lendl by No 4 Milos Raonic and first-timers No 6 Gael Monfils and No 8 Dominic Thiem.
His 122-week run as world number one has come to an end and Djokovic must out-perform Murray here to reclaim the position.
Thiem got the upper hand in the first-set tie break with a beautifully executed forehand down the line.
The Scot's opening round-robin clash at London's O2 Arena is against Croatian Marin Cilic.
While Djokovic and new world number one Andy Murray look set to dominate in 2017, the likes of Thiem, Germany's Alex Zverev, Australian Nick Kyrgios and several others are beginning to make inroads into the top echelons of the game. "It's not the first time I did it". "Even though I lost the first set, I thought I didn't do too many things wrong".
First up is Cilic, who beat Murray last time out in Cincinnati three months ago but has won just three of their 14 matches.
Djokovic survived three set points in the 76-minute first set before Thiem ripped a forehand victor.
"You guys are unbelievable", he said in the post match interaction when asked if he was concerned about the potential penalty for an incident where the ball went flying towards the stands.
"He went down a little bit and Andy got the mental boost from winning Wimbledon, I think that was the big key for him, and after that he's nearly been unstoppable".
"I have to obviously focus on myself, on my game, and implement as well a few tactical things I know from playing Andy".
"I started swinging more freely". "But first of all, it's a very good experience for me to play three matches against top-10 players".
"He congratulated me on a good season".
Milos Raonic was a victor on the opening day, beating Gael Monfils 6-3 6-4, while Jamie Murray and his Brazilian partner Bruno Soares defeated Treat Huey and Max Mirnyi 6-4 7-5 in the doubles.