However, Bastia were quick to restore parity as Francois Marque shot home in the 28th minute.
The home side did not lose heart after that, however, and regained their one-goal advantage five minutes before the half-time interval.
Mevlut Erding sent Pitroipa through on goal and the creator of the first goal made it 2-1 to Rennes.
Things seemed to go from bad to worse for Bastia nine minutes into the second half when Ilan Aruajo Dall'lgna was sent off for a second bookable offence.
The drama did not end there as six minutes from time Erding scored the winner for Rennes when he headed home Yann M'Vila's pass from outside the Bastia 18-yard box.