Question: Who did the professional tennis player currently ranked World No. 1 in men's singles defeat in the 2017 Barcelona Open Banco Sabadell - Singles?
Related documents: [0]  [DOC] Rafael "Rafa" Nadal Parera (] , ] ; born 3 June 1986) is a Spanish professional tennis player, currently ranked World No. 1 in men's singles. Known as "The King of Clay", he is widely regarded as the greatest clay-court player in history. His evolution into an all-court threat has established him as one of the greatest tennis players ever. [END] 
[1]  [DOC] Rafael Nadal was the defending champion and successfully defended his title, defeating Dominic Thiem in the final, 6–4, 6–1. [END] 
Answer: 
Dominic Thiem
Dominic Thiem