 A match between Eredivisie clubs Ajax and AZ in the fourth round of the 2011–12 KNVB Cup was replayed behind closed doors at Ajax's home ground, Amsterdam Arena, on 19 January 2012.In the original match, held at the same venue on 21 December 2011, Ajax held a 1–0 lead when a fan ran onto the pitch and launched a karate kick from behind against AZ goalkeeper Esteban Alvarado, who responded by attacking the fan before police and security arrived.When Alvarado was sent off for retaliating against his attacker, AZ left the pitch, and the match was abandoned.