Garcia's men are still confident of making up seven points on leaders Montpellier HSC with five games remaining.
However, the Frenchman said that his players must beat Carlo Ancelotti's charges at the Stade Lille-Metropole on Sunday.
"We're putting the pressure on PSG, but also on the sides below us, like Toulouse and Lyon. That said, we achieve this by focusing on our own performances," said the 48-year-old.
"It's an important win, because it takes us a step closer to guaranteeing a top-three finish. There are five matches left and 15 points up for grabs, so you never know what can happen.
"Still, Montpellier still have a seven-point lead over us, and getting past them will be very tricky. We're going to focus on the visit of PSG next Sunday."
Montpellier travel to Toulouse on Friday.