Complex sentence: In February 2005 he achieved a belated breakthrough in singles by winning the ATP event in Scottsdale, USA, which made him the oldest player ever to win a first ATP singles title (he was almost 34 at the time).
Split into simpler sentences: In February 2005 he achieved a belated breakthrough in singles by winning the ATP event in Scottsdale, USA. No other player in history has won his first ATP singles title at such an advanced age (Arthurs was almost 34 at the time).