The thing is, when push comes to shove contracts for professional sportspeople have to follow the same law as all (ok, most) other areas of employment.
Firstly, there has to be a reasonable resignation period. Even if an employee has a five year contract, it will stipluate the length of notice the employee has to give to terminate the contract. You simply cannot enforce a contract to it's end date, there legally has to be a period in which the employee can give notice to leave and then do so.
Secondly, Fages is claiming that the club were the first to breach their obligations under his contract, allowing him to leave immediately. Legally, it seems he is claiming constructive dismissal as the breach of contract on the club's part led to him being legally able to end the contract. This alleged breach could be monetary, but often constructive dismissal cases are brought under the "breach of mutual trust and confidence" argument, which could be open to many different interpretations and be for many different reasons. Usually, it's hard to defend or prove this as it is very subjectively based around the perspective of the employee. I would imagine the possible outcomes will be :
1. Fages takes the club to an Employment Tribunal for constructive dismissal. If he wins, the club will likely have to pay his loss of earnings between the end of his contract and his next employment.
2. The club will take Fages to court for Breach of Contract. This is extremely unlikely as even if the club win they will have to prove that they have suffered a direct financial loss to gain any kind of financial award, which would be very difficult in terms of a sporting organisation.
3. The club and Fages will come to some kind of settlement agreement. This is by far the best option for the employer and usually for the employee. This is what I would expect to happen.