Former world number one Novak Djokovic fell to a surprise defeat by Slovakian qualifier Martin Klizan in the second round of the Barcelona Open.

Klizan, ranked 140th in the world, beat 12th-ranked Djokovic 6-2 1-6 6-3.

The 12-time Grand Slam champion has failed to reach the last eight in any of his five tournaments since making his return from an elbow injury.

Defending champion Rafael Nadal progressed with a 6-4 6-4 win over compatriot Roberto Carballes Baena.

Spanish world number one Nadal has won 38 straight sets on his favoured clay surface.

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Nadal will face compatriot Guillermo Garcia-Lopez in the last 16.

Earlier, Japan’s Kei Nishikori retired from his second-round match against Garcia-Lopez.

Nishikori, who lost to Nadal in the Monte Carlo Masters final on Sunday, was trailing 6-3 before retiring with pain in his right thigh.

Bulgarian second seed Grigor Dimitrov beat France’s Gilles Simon 6-2 6-1, while Australia’s Dominic Thiem beat Spaniard Jaume Munar 7-6 (10-8) 6-1.

Spain’s Albert Ramos-Vinolas came from a set down to beat Brazil’s Rogerio Dutra Silva 3-6 6-3 6-4.