During a Dutch top-flight match on Sunday, former Newcastle defender Jetro Willems was punched by a supporter.
As a result of Sydney van Hooijdonk's goals, Heerenveen took a two-goal lead at Euroborg. The Z-side stand fans invaded the pitch in the 80th minute, overwhelming stewards.
Agroningen's players helped keep the peace by pleading with fans, including Willems. During this moment, a fan punched the former Netherlands international in the head.
Willems was escorted away by stewards unharmed. The left-back appeared to be comforted by some fans as referee Serdar Gozubuyuk sent the players back to the dressing rooms.
Play resumed after a lengthy delay, and Heerenveen won 2-0. Their visitors are ninth, while Eredivise is in the relegation zone. For the hosts, Willems played all 90 minutes.
The Groningen academy produced Virgil van Dijk and Luis Suarez.
Their bitter rivalry with Heerenveen, located in the north of the Netherlands, contributed to Sunday's unpleasant scene.