Petra Cetkovska (CZE) vs. Ana Ivanovic (SRB)[2]
Cetkovska lost most of her matches this year before winning two lower level claycourt tournaments beating players ranked mostly out of the top 200. 2007 French Open finalist Ivanovic is in another league right now.
Winner: Ivanovic

Agnieszka Radwanska (POL)[14] vs. Jelena Jankovic (SRB)[3]
These two players both have turned in some upsets of note in recent years. Both possess striking groundstrokes and have never played each other before. Jankovic is on a roll having won her last eight matches including taking the title in Rome, but she is fighting a sore right forearm. Radwanska of Poland won the Istanbul title prior to Paris and also brings a seven match winning streak into the round of sixteen match.

After Radwanska defeated world number one Maria Sharapova of Russia at the US Open last year she celebrated by purchasing herself a Louis Vuitton handbag. She would be able to afford several more designer bags should she upset Jankovic. I think she can if she pressures Jankovic and avoids long baseline rallies.
Winner: Radwanska

Paul-Henri Mathieu (FRA)[18] vs. Novak Djokovic (SRB)[3]
All of France will root for this upset. Can it happen? Of course it can but Mathieu would need to turn in a masterful performance which I think he will. The two players split their prior matches 1-1 and have never met on clay. Mathieu is only 18-11 in matches played this year, but can hit groundstokes with the best of them. He will need to attack before he is attacked and keep errors to a minimum.
Winner: Mathieu

Fernando Verdasco (ESP)[22] vs. Rafael Nadal (ESP)[2]
The king of clay Rafael Nadal of Spain is 24-0 at the French Open; having never lost a match in Paris and is 111 of 113 in his last claycourt matches. Spain meets Spain as Verdasco also of Spain tries to do the impossible. Verdasco won a set from Nadal on grass in 2006 but Nadal should roll on this surface where when he is healthy he looks unbeatable.
Winner: Nadal