Number-four seed Nikolay Davydenko, who has been tipped to challenge reigning champion Rafael Nadal and Federer for the title this year, booked his place in the French Open quarter-finals with a highly entertaining victory over David Nalbandian 6-3 7-6 (7/1) 3-6 7-6 (7/2).
The Russian, a semi-finalist here in 2005, claimed victory with a forehand winner, the first of his four match points in the last match on Philippe Chatrier court.
Davydenko will next play Canas, who won the battle of the Argentinians with some ease as he stormed to a straight-sets triumph over unseeded compatriot Juan Monaco.
The 19th seed, twice a quarter-finalist at Roland Garros, was a comfortable 6-0 6-4 6-2 winner on Suzanne Lenglen court in little more than two hours.
Canas is playing in his first grand-slam tournament in two years, having returned in September 2006 from a 15-month anti-doping suspension.
And he is thrilled with the way he is performing in Paris, even branding himself a genuine title contender.
The 29-year-old said: 'I think I am in my best form on clay.
'I'm very confident about my game. I'm playing my best tennis at the moment. I'm one of the people who can win the tournament.
'I'm happy with the way I played in all three sets here and there is no pressure on me.'
The other four last-16 matches, including Nadal's clash with gritty Australian Lleyton Hewitt, take place on Monday.
French Open fourth-round men's singles results in Paris on Sunday (prefix number denotes seeding).
4-Nikolay Davydenko (Russia) beat 15-David Nalbandian (Argentina) 6-3 7-6(1) 3-6 7-6(2)
19-Guillermo Canas (Argentina) beat Juan Monaco (Argentina) 6-0 6-4 6-2
1-Roger Federer (Switzerland) beat 13-Mikhail Youzhny (Russia) 7-6(3) 6-4 6-4
9-Tommy Robredo (Spain) beat 29-Filippo Volandri (Italy) 6-2 7-5 6-1
(Compiled by Infostrada Sports)
