With Neymar, Kylian Mbappe and Mauro Icardi missing out, Leandro Paredes was called up to the line-up alongside Moise Kean and Angel Di Maria.
The latter heeded the call in 11 minutes as Kean fired into the bottom-left corner from the edge of the area after Di Maria robbed Lea Siliki off possession before feeding his Italian counterpart.
An off-the-ball incident on Idrissa Gueye brought his evening to end after two minutes as the Senegalese went limping off the field and had Rafinha coming on in his place.
Di Maria reversed roles midway through the first half after running onto a through ball from Ander Herrera to lob over Rennes goalkeeper Alfred Gomis for the second goal.
PSG were forced into another change nine minutes before halftime with Thilo Kehrer going down off the ball before being replaced by Mitchel Bakker.
Rennes looked for a positive start to the second half through the likes of Steven N'Zonzi, Serhou Guirassy and Jeremy Doku.
The league leaders pushed for a third as the midway period approached, but Kean in particular and Rafinha failed to add their team's advantage.
Di Maria grabbed a second and his side's third after 73 minutes as the Argentine drifted to the edge of the area off a loose pass before rattling the bottom corner.
Rennes should've pulled a goal back minutes later from a one-on-one by Guirassy, but PSG goalkeeper Keylor Navas came up with an equally smart save as the defending champions held on for the clean sheet.