At 2006 Dubai Tennis Championships – Men's Singles, Rafael Nadal defeated the defending champion who has won how many Grand Slam singles titles?
2006 Dubai Tennis Championships – Men's Singles: Roger Federer was the defending champion but lost to Rafael Nadal in the final, 2–6, 6–4, 6–4. Roger Federer:  Federer has won 19 Grand Slam singles titles, the most in history for a male tennis player and has held the world No. 1 spot in the ATP rankings for a record total of 302 weeks, including a record 237 consecutive weeks.
19