A teary Grigor Dimitrov claimed the biggest scalp of his burgeoning career as he knocked world number one Novak Djokovic out of the Mutua Madrid Masters.

The 21-year-old Bulgarian, nicknamed 'Baby Fed', was treated to a standing ovation after he battled cramp to eventually come through a memorable three-hour second-round battle 7-6 (8/6) 6-7 (10/8) 6-3.

Djokovic was similarly impressed, repeatedly clapping his rivals throughout a contest in which he needed a 10-minute medical time out after rolling his ankle during the second set.

The Serb had seemingly recovered from the setback, though, when he saved a match point in the second set tie-break before going on to level the contest.

Dimitrov's challenge had also looked to be faltering when he was struck down by cramp during the tie-break, but he immediately recovered to break in the opening game of the deciding set.

He never looked back from there to further cement the comparisons that have been made between him and 17-time major winner Roger Federer.

Federer earlier returned from an eight-week break to ease into the third round with a 6-3 6-3 win over Czech veteran Radek Stepanek.

"I didn't think I played incredible, but that's not what I was expecting myself to do here. But I didn't play bad, either," said Federer.

"I'm very happy with how things went today."

Third seed Andy Murray needed two tie-breaks to see off Florian Mayer 7-6 (11/9) 7-6 (7/3).

"I didn't think I played incredible, but that's not what I was expecting myself to do here" - Roger Federer

The Scot had to save five set points in the opening tie-break before prevailing to win his first match since his early exit in Monte Carlo last month.

Stanislas Warwinka was Murray's conqueror on the Cote d'Azur and the 15th seed booked a second-round berth with a 6-4 6-4 win over Mariu Copil.

Frenchman Gilles Simon was the only other seed to go through today, beating countrymen Jeremy Chardy 6-4 7-6 (7/5) in their second-round contest.

Richard Gasquet (eight) headed the list of three seeds to fall with Janko Tipsarevic (nine) and Milos Raonic (12) bowing out.

Benoit Paire earned a second-round clash with Rafael Nadal as he beat Joao Souza 6-1 7-6 (7/0).