Question: At 2006 Dubai Tennis Championships – Men's Singles, Rafael Nadal defeated the defending champion who has won how many Grand Slam singles titles?
Sentence (from "Roger Federer"): Roger Federer (] ; born 8 August 1981) is a Swiss professional tennis player who is currently ranked world No. 2 in men's singles tennis by the Association of Tennis Professionals (ATP).
Relevant evidence: No