Angelique Kerber battled Svetlana Kuznetsova for two hours and 21 minutes in their fourth rounder.
It was Kuznetsova who survived, though, firing a forehand winner on match point to win, 64 46 63.
Serena Williams played just as hard - but maybe not as long - as she squared off with Roberta Vinci.
Williams reeled off the last 10 points of the match to move smoothly past the Italian, 61 63.
Carla Suárez Navarro looked like a world beater as she built a 75 42 lead against Sara Errani.
Errani was battling injury and some breathing problems, but worked her way back into the match.
Errani eventually returned to the French Open quarterfinals with a 57 64 63 win over the Spaniard.
The second wave of fourth round matches took the courts Monday, with Francesca Schiavone in action.
Schiavone stayed with Victoria Azarenka through the first six games, tying the first set, 3-all.
Azarenka completely took over from there though, reeling off nine straight games for a 63 60 win.
Over on Lenglen, Bethanie Mattek-Sands came out firing, building a 4-1 lead on Maria Kirilenko.
But Kirilenko brought out some spectacular shotmaking to fight back against the American, 75 64.
Maria Sharapova had a tough one but managed to overcome Sloane Stephens on Chatrier court, 64 63.
And in the last round of 16 match, Jamie Hampton took on a three-time French Open semifinalist.
And that three-time semifinalist - Jelena Jankovic - would eventually return to the quarterfinals.