World No. 1 Novak Djokovic survived a tough fourth-round to advance to the quarter-finals where he will be tested again, facing world no. 4 Marin Cilic.

The quarter-finals match will feature the defending Wimbledon champion taking on the U.S. Open champion.

Djokovic's path to defending his title was nearly shaken by South African Kevin Anderson who challenged the Serb in a match that began Monday and was continued Tuesday.

Anderson was the first true test for Djokovic as he won the first two sets 6-7(6) 6-7(6) and was on his way to the tournament's biggest upset.

But the world no. 1 was just warming up and bounced back taking the next two sets 6-1 6-4.

Djokovic had all the momentum and was on his way to staging a successful comeback until the match was stopped and suspended due to bad light. 

The fourth-round matchup between Djokovic and Anderson resumed Tuesday with the defending champion winning the last set 7-5 to clinch his quarter-finals berth against Cilic.

"Kevin served exceptionally well. This was one of the most difficult matches I have played at Wimbledon in my career," Djokovic said after the match.

The 28-year-old added, "It was high-quality tennis in the fifth set. At times I was helpless with my return - it was very difficult to read his serve and he was very aggressive. I was two sets down and coming back to win gives me great satisfaction and confidence for my next challenge."

Meanwhile Djokovic's opponent in the quarter-finals, Croatia's Cilic, defeated American Denis Kudla 6-4 4-6 6-3 7-5 to advance.

"I was not playing too great today. I would say just serving‑wise the level was a bit, a fraction lower than in my previous match," Cilic spoke about his match with Kudla according to Stevegtennis.com.

"But, I think Denis was playing really well. He was not missing much and had a little bit different game, and this court plays a bit faster than the other ones. So it was not easy. Especially since he had a few good wins," he added.

Cilic must pull all the stops against Djokovic who has his number as the defending champion holds a 12-0 lead in their head-to-head matchups.

The match will be at Centre Court this Wednesday, following Andy Murray's quarter final game, which has a start time of 1 p.m. BST (8 a.m. EST).

For other match schedules click here and you can watch the match online through live stream by clicking here.