Top seed Kei Nishikori stunned by home favourite Thomaz Bellucci in the first round of the Rio Open

The world number 5 lost in straight sets to Bellucci, 6-4 6-3

Nishikori had his serve broken four-times (Getty)

World number five Kei Nishikori was dumped out in the first round of the Rio Open by home favourite Thomaz Bellucci.

The top seed went down 6-4 6-3 on the clay in Brazil, having his serve broken four times by Bellucci.

Nishikori's exit opens things up nicely for second seed Dominic Thiem, who progressed past Janko Tipsarevic 6-4 7-5.

2015 champion David Ferrer is out, though, as he lost to Alexandr Dolgopolov in straight sets, but there were victories for Fabio Fognini, Thiago Monteiro, Pablo Carreno Busta, Albert Ramos-Vinolas amd Federico Delbonis.

World number four Milos Raonic enjoyed safe passage to the second round of the Delray Beach Open.

Former winner Ferrer lost to Dolgopolov (Getty)

The Canadian, seeded first, breezed past American Tim Smyczek 6-1 6-4 to set up a second-round clash with Borna Coric.

Second seed Ivo Karlovic is out after he was beaten in a tight game by Donald Young, who triumphed 7-6 (7/5) 7-6 (7/3), while third seed Jack Sock is through after a 6-4 7-6 (7/2) win over Radu Albot.

Juan Martin del Potro, Steve Johnson, Steve Darcis, Guillermo Garcia-Lopez and Nikoloz Basilashvilli were also first-round winners.

Fabio Fognini also qualified for the next round (Getty ) (Getty)

Frenchmen Nicolas Mahut, Richard Gasquet and Julien Benneteau were among the winners at the Open 13 in Marseille.

Mahut defeated Germany's Alexander Zverev 7-6 (7/5) 7-6 (7/5), Gasquet beat Robin Haase of Holland 6-7 (5/7) 6-3 6-2 and Benneteua defeated Canadian wildcard Denis Shapovalov 7-5 6-4.

Aljaz Bedene of Great Britain, Slovakia's Norbert Gombos, Germany's Jan-Lennard Struff and Ukrainians Illya Marchenko and Sergiy Stakhovsky also advanced.