Ethan Nwaneri avoided a red card for Marseille after a lunging challenge on a fellow Arsenal academy graduate on Tuesday night.
Nwaneri, 18, joined the French club on loan from Arsenal in the January transfer window and was in cup action for his new side when he might have been sent off.
Marseille defeated Rennes 3-0 in the Coup de France quarterfinals after goals from Amine Gouiri, Mason Greenwood and Pierre-Emerick Aubameyang.
But after 22 minutes, at 1-0, Nwaneri slid in and caught Rennes' Glen Kamara.
He was booked, frustrating the away side who wanted a harsher punishment for the teenager.
VAR is not used at this stage of the French cup competition.
Rennes boss Habib Beye (the former Newcastle United defender) and Marseille counterpart Roberto de Zerbi exchanged words after the incident.
Kamara, injured, had to be substituted nine minutes later.
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Kamara came through the Arsenal academy a decade before Nwaneri's emergence.
But he only made a single competitive appearance for Arsenal, in the League Cup fourth round in 2015.
After loans at Southend and Colchester, he moved to Dundee in Scotland before making his name with Rangers.
Kamara spent a season with Leeds United in the Championship before switching to Rennes in 2024, where he has returned to after a loan at Al Shabab in Saudi Arabia.
