A thrilling first half saw Rennes take the lead with the first shot of the game, as Valentin Rongier cut back for Esteban Lepaul to lash home.
That gave the visitors the springboard to dominate proceedings, with Musa Tamaari striking over from the edge of the box shortly before squaring for Sebastian Szymanski to double Les Rouge et Noir’s advantage with a deflected effort.
Arnaud Nordin could have put Rennes even further ahead before the half-hour mark, dragging a shot wide from an acute angle prior to slipping at a vital moment in the area to allow Yehvann Diouf an easy save.
However, against the run of play, Nice had the ball in the net with their first attempt of the match through a delicate finish from Morgan Sanson.
Ultimately, though, he was denied a sixth Ligue 1 goal contribution against Rennes, given Mohamed-Ali Cho was offside in the build-up.
The Eagles’ predicament then got worse when the visitors were awarded a penalty after Melvin Bard fouled Tamaari in the box, but Diouf was equal to Lepaul’s strike to keep his side in the game - although Tamaari headed in the rebound, Nice received another let off as it was ruled out due to encroachment.
Both goalkeepers then made important saves to keep the score toward the end of the opening period. First, Brice Samba stopped Cho’s attempted lob before Diouf parried away a fierce Rongier strike.
Determined to get back into the game, the hosts made two changes at the break, and one of them, Kail Boudache, saw his powerful drive tipped over by Samba.
However, Rennes were still dangerous themselves and Tamaari, in particular, was desperate to get on the scoresheet after such an influential first-half performance.
Nevertheless, Nice were on top after the interval and really should have halved the deficit when Kevin Carlos glanced a free header off target from close range. Then, Tom Louchet’s acrobatic effort clipped the crossbar as Les Aiglons appeared to be close to halving the deficit.
In response, though, Rennes made a triple substitution to freshen up the team, and it paid off as two of the replacements combined to seal all three points.
While Breel Embolo will be credited with the assist, the goal was all about Ludovic Blas, who went on a mazy solo run before eventually cutting the ball back into the far corner.
Adding extra gloss to the scoreline, fellow sub Nordan Mukiele curled past a helpless Diouf in stoppage time in a win that sees Rennes break into the European places.
Nice, meanwhile, still linger just above the relegation zone after a seventh successive Ligue 1 game without a win (D4, L3) - only five points separate them from the play-off spot.
Flashscore Man of the Match: Musa Tamaari (Rennes)
