Novak Djokovic may not have been at his best this evening but the Wimbledon top seed still managed to beat Tommy Haas in straight sets and secure a place in the quarter-finals.

Having seen fellow world number one Serena Williams felled earlier on Centre Court, the 26-year-old Serbian ensured he would not follow suit on the day in the tennis year commonly known as 'Manic Monday'.

Djokovic won his toughest clash of the tournament 6-1 6-4 7-6 (7/4) in two hours and 12 minutes as 35-year-old Haas provided the "big challenge" he had predicted.

It had looked like it would be another easy outing for the top seed at the All England Club, with the six-time grand slam champion taking the first set in just 25 minutes.

However, world number 13 Haas responded strongly and became the first player in this tournament to break Djokovic's serve - a feat he achieved in both the second and third sets.

Yet it was not to be for Haas, as Serbian Djokovic secured progress to a 17th consecutive grand slam quarter-final after a tie-break in the decider.

Veteran Haas was bidding to become the oldest quarter-finalist since Tom Okker in 1979 and showed great determination.

Rather than wilt after a one-sided first set, the Florida-based German responded impressively and made his breakthrough on the Djokovic serve in the fifth game of the second set.

The one-time Wimbledon semi-finalist held serve to go 4-2 up, only for Djokovic to come powering back and take the second set in 49 minutes.

Djokovic, 26, looked composed and in control when play resumed, showing an impressive array of shots that kept Haas guessing.

The 13th seed did his best to keep up and recovered well after losing serve, breaking back as Djokovic served for the match.

It merely delayed the inevitable, as the world number one won the tie-break that soon followed to set up a quarter-final clash with seventh seed Tomas Berdych.