Lemina was dismissed six minutes from time in Marseille's 1-1 Ligue 1 draw at the Stade de Route de Lorient in an incident that could prompt strong action from the French league.
The ex-Lorient man was tussling for the ball with Swede Toivonen - who had put Rennes ahead in the 27th minute - when he reacted to receiving a kick in the back by launching a jab into the striker's groin.
Referee Amaury Delerue was left with no choice but to dismiss Lemina and, with the Ligue de Football Professionnel's (LFP) disciplinary panel deciding sanctions on a case-by-case basis, the Gabonese could now be hit with a hefty ban.
The LFP have a history of handing down stern punishments for violent offences, one of the most notable in recent times coming back in September, when Bastia striker Brandao was punished with a six-month ban for headbutting Paris Saint-Germain's Thiago Motta in the tunnel at the Parc des Princes.
Lucas Ocampos had earlier cancelled out Toivonen's strike with a goal on his debut in the 60th minute prior to Lemina's moment of madness.
Marseille are now a point behind Lyon - who meet defending champions Paris Saint-Germain on Sunday - at the top of Ligue 1.
