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?

Context paragraphs:
2011 Barcelona Open Banco Sabadell: The 2011 Barcelona Open Banco Sabadell (also known as the "Torneo Godó") was a tennis tournament played on outdoor clay courts.  It was the 59th edition of the event known this year as the Barcelona Open Banco Sabadell, and was part of the ATP World Tour 500 series of the 2011 ATP World Tour.  It took place at the Real Club de Tenis Barcelona in Barcelona, Spain, from April 16 through April 24, 2011.  The defending champion was Fernando Verdasco, but was absent from the tournament in 2011.

Rafael Nadal: 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.

2013 Barcelona Open Banco Sabadell: The 2013 Barcelona Open Banco Sabadell (also known as the "Torneo Godó") was a men's tennis tournament played on outdoor clay courts.  It was the 61st edition of the event and it was part of the ATP World Tour 500 series of the 2013 ATP World Tour.  It took place at the Real Club de Tenis Barcelona in Barcelona, Catalonia, Spain, from 20 April through 28 April 2013.  Rafael Nadal won his record 8th title at the tournament.

2010 Barcelona Open Banco Sabadell: The 2010 Barcelona Open Banco Sabadell (also known as the "Torneo Godó") was a tennis tournament played on outdoor clay courts.  It was the 58th edition of the event known this year as the Barcelona Open Banco Sabadell, and was part of the ATP World Tour 500 series of the 2010 ATP World Tour.  It took place at the Real Club de Tenis Barcelona in Barcelona, Catalonia, Spain, from April 19 through April 25, 2010.

2011 Barcelona Open Banco Sabadell – Singles Qualifying: 2011 Barcelona Open Banco Sabadell – Singles Qualifying

2017 Barcelona Open Banco Sabadell: The 2017 Barcelona Open Banco Sabadell (also known as the "Torneo Godó") was a men's tennis tournament played on outdoor clay courts.  It was the 65th edition of the event and part of the ATP World Tour 500 series of the 2017 ATP World Tour.  It took place at the Real Club de Tenis Barcelona in Barcelona, Catalonia, Spain, from April 24 through April 30, 2017.

2012 Barcelona Open Banc Sabadell: The 2012 Barcelona Open Banco Sabadell (also known as the "Torneo Godó") was a men's tennis tournament played on outdoor clay courts.  It was the 60th edition of the event and it was part of the ATP World Tour 500 series of the 2012 ATP World Tour.  It took place at the Real Club de Tenis Barcelona in Barcelona, Catalonia, Spain, from April 23 through April 29, 2010.  Rafael Nadal won the singles title.

Barcelona Open (tennis): The Barcelona Open (currently sponsored by Banc Sabadell) is an annual tennis tournament for male professional players.  The event has been held in Barcelona, Catalonia, Spain every year since 1953, and is played on clay courts at the Real Club de Tenis Barcelona.  It was an event of the Grand Prix tennis circuit between (1970–1989), except in 1971 when it was part of the World Championship Tennis (WCT) circuit, although it was also open to non-WCT players.  The tournament is part of the 500 series on the ATP World Tour.  It is also known as Torneo Godó, Trofeo Conde de Godó, and Open Banc Sabadell.

2017 Barcelona Open Banco Sabadell – Singles: Rafael Nadal was the defending champion and successfully defended his title, defeating Dominic Thiem in the final, 6–4, 6–1.

2009 Barcelona Open Banco Sabadell: The 2009 Barcelona Open Banco Sabadell (also known as the "Trofeo Torneo de Godó") was a men's tennis tournament played on outdoor clay courts.  It was the 57th edition of the event known that year as the Barcelona Open Banco Sabadell, and was part of the ATP World Tour 500 series of the 2009 ATP World Tour.  It took place at the Real Club de Tenis Barcelona in Barcelona, Spain, from 20 April through 26 April 2009.

Supporting paragraphs: 2017 Barcelona Open Banco Sabadell – Singles Rafael Nadal
Answer: Dominic Thiem