Gelson Martins is among five members of the Sporting squad attempting to terminate their contracts, according to reports.
Arsenal have shown an interest in the Portugal international winger and a number of other English clubs have been monitoring him.
Goalkeeper Rui Patricio and winger Daniel Podence are alleged to have handed in their resignation last week, while Martins, William Carvalho – previously a target for West Ham – and Bruno Fernandes have now reportedly followed suit in attempting to cancel their contracts.
It leaves Sporting seemingly facing the possibility of losing several of their top players for no fee.
The resignations follow an incident at the club’s training ground last month in which a group of fans attacked several players in the wake of Sporting’s failure to qualify for next season’s Champions League.
Former Sporting full-back Fernando Mendes told Radio Renascenca, in quotes reported on www.record.pt: “After Patricio and Podence left, things calmed down a little bit. Now, from one moment to the next, three players with this importance (leave) … I’m very pessimistic.”
Former Sporting presidential candidate Carlos Severino was among those to criticise current incumbent Bruno de Carvalho for his handling of the affair.
“I have been in a constant state of anxiety for a long time,” he told CMTV.
“Sporting Clube de Portugal is in danger of being kidnapped by someone who owns Sporting Clube de Portugal. The club is crumbling.”
Former club director Isabel Trigo Mira told the same station: “I’m not surprised because I figured they would do it – they are players that we have as big assets, but they are assets that are going to be lost.
“I do not know where this is going or what is expected to happen. I hope someone opens their eyes and finally does something, because Sporting cannot continue as it is.”