Rafael Nadal and Roger Federer through to quarterfinals of Qatar Open . No . 1 Federer taken to 1 sets by unheralded Belgian Nikolay Davydenko . Nadal also survives scare to beat his close friend Marco Chiudinelli . Big-serving Croatian Ivo Karlovic won an epic match against German eighth seed Philipp Kohlschreiber , triumphing 7-6 ( 7-5 ) 6-7 ( 2-7 ) 7-6 ( 7-4 ) to set up a quarterfinal with Russia 's defending champion Nikolay Davydenko . Defending champion Nikolay Davydenko also seeking to reach the last eight .
Rafael Nadal and Roger Federer through to quarterfinals of Qatar Open . No . 1 Federer taken to 1 sets by unheralded Belgian Nikolay Davydenko . Nadal also survives scare to beat his close friend Marco Chiudinelli . Defending champion Nikolay Davydenko also seeking to reach the last eight .