Complex sentence: On 11 May 2010, Riveros signed for Sunderland on a three-year-deal, saying The league is very competitive and I look forward to being very successful with Sunderland.
Split into simpler sentences: On 11 May 2010, Riveros signed for Sunderland on a three-year-deal. He has said The league is very competitive and I look forward to being very successful with Sunderland.