World No 1 Novak Djokovic has admitted he was “shocked” by his Australian Open semi-final performance, after his 54 unforced errors helped Jannik Sinner to victory in four sets at Melbourne Park on Friday.

The Serbian had not lost at the tournament for 2195 days, but found himself down two sets inside 74 minutes against the Italian. “I was, in a way, shocked with my level, in a bad way,” he said. “This is one of the worst grand slam matches I’ve ever played, at least that I remember.”

The 10-time Australian Open champion said his opponent played a “flawless match”. Djokovic failed to muster even a single break point chance across the three-hour, 22-minute duel. “Obviously if you serve well and if you don’t face a break point, it plays with the mind of your opponent, meaning you can put more pressure on his service games – my service games in this case – and you kind of swing freely,” he said.

The 36-year-old said he was “not playing up to par” throughout the tournament, and that he doesn’t know whether he will be able to return to his previous level. “This tournament hasn’t been, as I said, up to my standard or criteria or the level that I would normally play or expect myself to play, but doesn’t necessarily mean that it’s beginning of the end, as some people like to call it.”

Sinner said it was a “tough match”, made more difficult when he failed to convert a match point in the third set tie-break. “It’s not easy, because you are so close and then you, in your mind … the way is long still,” he said. “But in the other way, I sat down, I tried to think also that the score was two sets to one for me, so it was positive.”

The 22-year-old said he spotted early that his opponent’s game was off, but also that Djokovic could find his form – and especially his dangerous return – at any time. “I realised, especially the first sets, he was not playing that great, but I tried to have the intensity as high as possible, and I took the chance,” said Sinner.

Although Sinner secured the most significant victory of his career, he was not outwardly emotional after the match. “I feel these kind of emotions you cannot control,” he said. “In my mind today I knew it was semi-final. It’s not that you win the tournament like this, so I’m looking forward for Sunday, and let’s see what’s coming.”

Friday’s result was Djokovic’s first ever defeat in the semi-finals at the Australian Open, and it means his Sunday in Melbourne will be a little bit different. “I still have high hopes for other slams, Olympics, and whatever tournaments that I’ll play, it’s just the beginning of the season,” he said. “It’s not the feeling that I’m used to.”

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