Spain's five-times winner Nadal started this tournament very slowly indeed for his standards but is gradually finding his form while Swedish fifth seed Soderling has been solid if unspectacular so far.
Sparks could fly though in the last-eight match given the rivalry even if focus is already shifting towards a luscious semi-final between rampant Novak Djokovic and record 16-times Grand Slam champion Roger Federer later in the week.
Having shrugged off Viktor Troicki in five sets and an ankle tendon tear on Tuesday, Andy Murray is in action for a third straight day in his quarter-final against Juan Ignacio Chela.
The Argentine, 31, is the only unseeded player left in either singles draws but has never got past this stage at Roland Garros before just like the British fourth seed.
"I've done a lot of icing, been taking a lot pills. I had an MRI scan, had an ultrasound scan," Murray said about his battle to get his ankle ready for Troicki and now ready for Chela and possibly ready for Nadal or Soderling in the semi.
Before the men take to the red clay, which was swirling into the players' eyes during high winds on Tuesday when Federer blew past Gael Monfils in his quarter-final, sixth seed Li Na battles Belarus' Victoria Azarenka in a women's last-eight match.
Li is the first Chinese player to reach this point in Paris and will not give up without a fight judging by her determined displays in the previous rounds, even if fourth seed Azarenka has been in superb form for months.
The winner will play either seventh seed Maria Sharapova or German 15th seed Andrea Petkovic, who meet on Court Suzanne Lenglen in their last-eight clash with the Russian leading the head-to-head 2-1.
Home hope Marion Bartoli and holder Francesca Schiavone won through on Tuesday to set up a last-four meeting.