Unbeaten in their previous four home League games, Strasbourg started the stronger and should’ve opened the scoring on 15 minutes with the first clear-cut chance of the game.
Chelsea loanee David Datro Fofana burst through on goal and rounded the goalkeeper, but he lost his composure and tamely struck the ball at the retreating Abdelhamid Ait Boudlal, who made a timely goalline clearance.
That was a pivotal moment in the half, as the visitors quickly took control, creating numerous chances.
Musa Al-Taamari looked particularly dangerous for Rennes with his pace, but Mike Penders was able to smother his effort after a terrific burst of pace opened up the shooting chance. Despite an impressive first half, Penders was at fault for the opening goal, as a poor kick-out was aimed straight at Sebastian Szymanski.
The Polish midfielder acted quickly to divert the ball to Esteban Lepaul, who found the bottom corner for his 17th Ligue 1 goal of the season.
Penders did atone for that with a strong double save to deny Al-Taamari and Ludovic Blas, but the hosts went into the break deservedly behind.
Instead of finding a quick response after the break, Gary O'Neil’s side quickly fell apart as they conceded two quick-fire goals. The first saw Lepaul turn provider as his flicked a header towards goal that may well have been going in, but Breel Embolo made sure as he chested home on the goalline.
Less than two minutes later is was 3-0, with Al-Taamari finally getting his reward with a clinical finish after being slipped in on goal by an incisive pass from Blas.
Needing a reaction, Strasbourg made a triple substitution just before the hour mark, and almost found a way back into the game when Martial Godo struck the post with a mishit volley.
Ultimately, they couldn’t find a way back into the game, and the three points bring Rennes within one point of third-placed Lille, further fuelling their hunt for UEFA Champions League football next season.
The defeat further consigns Strasbourg to a likely mid-table finish, as they remain eight points outside the top six, perhaps allowing them to focus further on their UECL campaign.