Sydney FC chief executive Tony Pignata has condemned online trolls attacking midfielder Ali Abbas on twitter by celebrating his horrendous knee injury and taunting the player directly via social media.

The Iraqi-born midfielder was subject to a barrage of abusive tweets from Western Sydney Wanderers fans in the wake of suffering a season-ending knee injury in Saturday night's derby. Abbas limped off the field early in the match after tearing his anterior cruciate ligament and medial ligament in his left knee suffered as a result of a dangerous challenge from Wanderers player Iacopo La Rocca.

Ali Abbas writhes in pain after tearing his anterior cruciate ligament and medial ligament in his left knee. Credit:Getty Images

Some rival fans welcomed news of the injury by celebrating online and posting provocative messages and images, sending them directly to the player on social network sites.

The disgraceful comments prompted Sydney FC's chief executive to publicly condemn the trolls revelling in a long term injury to one his club's star players.