Novak Djokovic says he is “trying to solve the riddle” and find his best form after fighting back from a set down to beat American qualifier Zachary Svajda in the US Open second round.
The 24-time Grand Slam champion appeared subdued in the early stages of the match before powering through to a 6-7 (5-7) 6-3 6-3 6-1 win.
“I’m not pleased with my level of tennis, but, you know, you have days like this where you’re not playing at your best, but you just kind of find a way,” Djokovic said.
“I’m just trying to solve the riddle once I’m on the court.”
The 38-year-old said he was “a bit with frustrated with his game” as he continues his bid for a standalone record 25th major trophy.
“It’s not like I’m not finding joy on the court competing. I enjoy competing, but I don’t enjoy not playing well,” the Serb said.
“That’s why I put extra pressure on myself and my team to be better the next day, the next match,” he said.
“It’s not a motivation thing. I kind of go through stuff internally. You don’t want to know the details of what I’m going through and telling myself.”
Djokovic has already set another record in New York in reaching the third round at a major for the 75th time – one more than Roger Federer’s tally.
He will face Britain’s Cameron Norrie – who he has beaten at the French Open and Wimbledon this year – in the third round.