In those 20 minutes, he scored a fine goal and demonstrated exactly why PSG will wrap up the Ligue 1 title and challenge in the Champions League this season.
Laurent Blanc has a squad at his disposal which can rival the very best and in players such as Cavani has the individual talent to beat any side in Europe.
Sunday evening's match was the first time Cavani had appeared in a PSG squad for more than a month. His last outing for Les Parisiens was in the 2-0 win at home to Girondins de Bordeaux in January; a niggling hamstring injury hampering his return to action.
4 - Edinson Cavani is the most prolific substitute in Ligue 1 this season with four goals after coming off the bench. Impact.— OptaJean (@OptaJean) March 3, 2014
What will be particularly pleasing to PSG fans, not to mention Cavani himself, is the way in which the Uruguayan slotted seamlessly back into the PSG attack, finding the back of the net on his return.
It took PSG's No. 9 less than 10 minutes to get on the scoresheet. Cavani replaced fellow South American Ezequiel Lavezzi on the 70-minute mark and rounded off a flowing move in the 79th minute to seal a deserved victory.
A high ball over the Marseille defence found Gregory van der Wiel romping forward down the right flank, and the full-back expertly volleyed a first-time cross into the area for Cavani to run on to.
El Matador made no mistake, leaping unchallenged to direct a powerful header past the helpless Steve Mandanda into the right-hand corner of the net.
This was Cavani's 14th Ligue 1 goal of the campaign, a season in which he has settled well into the Parc des Princes. Zlatan Ibrahimovic remains undisputedly PSG's talisman, but Cavani has played an important role since his arrival from Napoli in the summer.
Between them, Ibrahimovic and Cavani have amassed 36 goals in the league, more than third-placed Lille have scored in total.
Statistics such as this demonstrate the quality that PSG have this season. To challenge at the top of European football, a club needs not only a strong starting 11, but a strong squad. Laurent Blanc has such a unit at PSG, and the current crop of players could feasibly go all the way to the Champions League final in May.
In Le Classique, the three substitutes introduced by Blanc were Cavani, Pastore and recent arrival Yohan Cabaye. Of those three, Cavani is the one who stands out, but the other two players would walk into the starting line-up of any other Ligue 1 side, not to mention most sides across the top European leagues.
The embarrassment of riches at Blanc's disposal means that the Ligue 1 title is the minimum PSG should achieve this year.
Le Classique was sealed by Cavani's header and, in truth, so was Ligue 1. Going into the 27th round of matches, PSG were already five points clear of their only realistic title rivals, AS Monaco.
Claudio Ranieri's side suffered a devastating 2-0 defeat to fourth-placed Saint Etienne, after which Ranieri conceded that the title would remain in Paris for another year.
PSG's win confirmed their title credentials, and the yawning eight-point gap that lies between the two clubs now means that a second consecutive Ligue 1 crown is almost a certainty. Cavani's return should see PSG move up another gear as the season enters its closing stages.
Les Parisiens have all but sewn up the league, are firm favourites in the final for the league cup and have one foot in the Champions League quarter-finals.
With the strength and quality in the squad, particularly in the form of the returning Cavani, PSG have the opportunity to have a historically successful season.