Sporting Lisbon ultras infiltrated the club's training ground facilities, and attacked their own striker Bas Dost in absolute shocking scenes.
Reports surfacing from Portugal claim a group of around 50 hooligans, who covered their faces, invaded the club's training base, and went at staff as well as players.
Manager Jorge Jesus, captain William Carvalho and vice-captain Rui Patricio were believed to be targeted. The aforementioned players are reportedly seeking to cancel their contracts.
The pair of internationals were recently named in Portugal's provisional World Cup squad.
Furthermore, the Sporting players are set to make a police report, they say they will not play in Sunday's Portuguese Cup final.
While Sporting Lisbon's skipper and vice captain weren't injured, the same cannot be said about Dost.
The Dutch international sustained injuries to his leg, not to mention suffering nasty cuts on his head.
Extremely bizarre considering his goal-scoring heroics this campaign, chipping in with 27 league goals.
The club's physio was also attacked who got stabbed in the leg. While attackers trashed the changing rooms, too.
Naturally Dost is shocked about the disgraceful act.
"I have no words, I was not expecting this situation, it was a distressing situation and we are all shocked," he told Ojogo.
"This is a drama for everyone, I am empty."
Primeira Liga reacted, releasing a statement calling the so called fans 'criminals'.
"The violent acts the players and coaching staff of Sporting Lisbon were subject to today.
"The perpetrators of these incidents are not fans of football, they are criminals."
As for Sporting Lisbon, a statement was delivered condemning what it calls: "acts of vandalism and the attacks on [our] athletes, coaches and professional staff."
Reports suggest police detained 21 suspects a few hours removed from the unsavoury incident.
As mentioned, Sporting Lisbon were going through their paces ahead of Sunday's cup final.
Security has increased for the game versus Aves.