BARCELONA (AFP) - US Open tennis champion Marin Cilic's disappointing season continued, as he was dumped out of the Barcelona Open by Dominican Victor Estrella Burgos 6-4, 6-4 on Wednesday.

The Croat's normally relentless serve let him down, as the world No. 53 broke four times in 10 Cilic service games to seal a place in the last 16 against Juan Monaco or Martin Klizan.

Cilic's start to the year was hampered by injury as he missed the Australian Open, but he has won just two matches in three tournaments since his return in Indian Wells last month.

Santiago Giraldo set up a third-round meeting with top seed and defending champion Kei Nishikori with a 6-3, 3-6, 6-1 over Portugal's Joao Sousa.

Rafael Nadal begins his campaign for a ninth title in Barcelona later on Wednesday in a rematch with Nicolas Almagro, who ended the 14-time Grand Slam champion's 41-match winning streak in the Catalan capital in last year's quarter-finals.