Complex sentence: He is now Canada's top-ranked singles performer, according to the ATP, having been Canada No.2 from August 4,2008 until June 21,2010 (with the exception of one week).
Split into simpler sentences: He is now Canada's top-ranked singles performer, according to the ATP, having been so since June 21,2010. Previously he was Canada No.2 from August 4,2008 until June 21,2010 (with the exception of one week).