 Federer and Nadal have been playing each other since 2004 , and their rivalry is a significant part of both men 's careers . 
 Federer and Nadal have been playing each other since 2004 , and their rivalry <a href='drop_aux' title='1'><mark>is</mark></a>a significant part of both men <a href='null_genetive' title='2'><mark>'s</mark></a>careers . 
Federer and Nadal have been playin each other since 2004 , and their rivalry a significant part of both men  careers .