Novak Djokovic heaped praise on Dominic Thiem after the Austrian defeated him at the Nitto ATP Finals on Wednesday in London.

The current No. 4 Thiem, who was trailing by a set, displayed unbelievable skills to take the match 6-7 (5), 6-3, 7-6(5) in the Group Bjorn Borg and secured a place in the last-four round. With this victory, Thiem has now defeated the former World No. 1 as many as four times in their past five meetings.

Djokovic certainly was outplayed in his second Round-Robin match at ATP Finals 2019 and the Serbian did not hesitate to acknowledge his opponent's brilliant game.

"I don't think I have experienced too many matches like this where my opponent just goes for every single shot. He was unbelievable, and in some stages, it was just incredible that he was just literally smacking the ball as hard as he could and [it] was going in," Djokovic added.

Novak Djokovic celebrates winning the first set against Dominic Thiem during their round-robin match at the ATP Finals
Novak Djokovic celebrates winning the first set against Dominic Thiem during their round-robin match at the ATP Finals AFP / Glyn KIRK

After winning a set each, Thiem and Djokovic headed into a tie-break in the decider third set. Having won his past nine tie-breaks, Djokovic was clearly the favorite to take the match. However, Thiem, who smashed 51 winners on Wednesday, ensured Djokovic's streak broke.

"He was taking every opportunity to smack the ball as hard as he could. Flatten it out, backhand down the line. He didn't miss too many backhands down the line, really. It was amazing. I have played him before. I know his game. But what he did tonight was just out of ordinary," Djokovic said of Thiem in an interview with ATP.

"I know that he can play at a high level, but tonight was just phenomenal. I had to fight, and I did. I'm proud of coming back from 5-6 down [in the third set]. He was serving for the match. I had a tie-break. I was [3/0], serve, 4/1 up, 5/4, you know, maybe should have played a little more aggressive in those moments, but credit to him," Djokovic, who is a five-time ATP Finals winner, added.

Both Djokovic and his Group Bjorn Borg member Roger Federer have fallen to 1-1 at the ATP Finals and are set to face each other on Thursday to clash for a semi-final spot. According to their ATP Head to Head, Djokovic leads 26-22 and has won their past four fixtures as well.

Meanwhile, for Djokovic to end the year as the top-ranked ATP player, current No. 1 Rafael Nadal must not make it to the final and at the same time, he will have to win the ATP Finals 2019. In another scenario, if Nadal fails to win a Round-Robin match, all Djokovic will have to do is reach the final. In that case, even if the Serbian lost the final, he still would clinch the top rank at the end of the year.