A flashpoint in the 39th minute overshadowed the match and brought an early end to referee Mathilde Demoncay's evening.
It started with a foul on Fortuna forward Lequincio Zeefuik. An opponent tugged the young striker's shirt and he then allowed himself to be drawn into a fierce reaction. Within seconds, the situation descended into chaos as more and more players from both teams piled in.
Trying to restore order and cool tempers, the referee ended up right in the middle of the melee. Demoncay lost her footing, fell to the pitch and suffered a mild concussion. She was never going to continue after the interval.
In friendly: referee knocked out in mass confrontation
Her injury forced an unusual reshuffle in the officiating team after half-time: one of the assistant referees stepped in to take charge for the second half and saw the match through to the end.
On the touchline, a spectator stepped in to fill the gap. He is an active amateur referee and took over with the flag for the rest of the match.
Sittard and Metz start their seasons soon
On the pitch, the game ended in a 3-1 win for the team from France. For the Sittard side coached by Danny Buijs, it was the penultimate friendly of their summer preparations.
Next Friday, Sittard face Cypriot side APOEL Nicosia in their dress rehearsal before their Eredivisie campaign begins on 8 August with an away game at PSV Eindhoven.
Metz, meanwhile, take on 1. FC Kaiserslautern on 1 August. Their Ligue 2 season starts a week later at home to EA Guingamp.