The German players' union has advised Kevin-Prince Boateng and Sidney Sam to take action against Schalke after they were handed indefinite suspensions.
Boateng, 28, and Sam, 27, were both ordered to stay away from the club on Monday, with the club hierarchy saying they had a negative effect on the team, who have been on a dismal run of form that could yet see them fail to qualify for next season's Europa League.
Boateng is under contract for one more season and had been widely expected to leave the Royal Blues this summer after falling out of favour under coach Roberto Di Matteo, while Sam, who only arrived at the club last summer, has three years left on his current deal.
Schalke will continue to pay both players' salaries until they are either sold on to a new club or their contracts are annulled, although they will not receive bonuses. A report in Sport Bild last week said that Boateng earns an annual salary of €7.5 million including all bonuses, while Sam receives €4m, also including bonuses.
German players' union VDV, though, has urged the two players to take action against the club to avoid a negative effect on their careers if the matter is not swiftly resolved.
"Provided the players are not integrated into the squad in a timely fashion, the VDV will advise them to take legal action against their employer," a press release published on the official VDV website said. "There is no legal basis to gratuitously exclude players from the match or training operations."
It said the players would have "excellent prospects for success in court" and added: "In the past there have been many professionals who did not fight against their employers out of fear and subsequently had problems on the market."
Meanwhile, Schalke chief Clemens Tonnies, who had publicly backed sporting executive Horst Heldt's decision to suspend the duo, has said he remains hopeful the club will complete a deal for Sami Khedira.
The Germany international is set to leave Real Madrid on a free transfer this summer and Schalke had suggested they were confident of a deal earlier this year.
The club's failure to make the Champions League had made a deal less certain, but Tonnies told Sky: "We have received signals that he would like to join Schalke, and we hope that it works out. I see a very good chance that he will opt for Schalke."
However, Tonnies rejected reports that a deal was already in place.