And relating to the topic, if a player didn't play for certain matches I think it will affect their salary and contracts. I'm not so sure about how it works but there's also some incentives and as well as deductions basing on their performances.
It could possibly be or someone who knows how contract works can explain more of it.
There will be no deduction of salary based on their performance as that is already in the contract, but if they will not perform well, they might be traded or they will not be re-signed when the contract expires. However for incentives, it's possible as that's additional compensation for the player, no one would complain that as it does not violate a contract.
Obviously, there's an expiry for the contract and it can be renewed if the management and the player agrees.
They probably include the incentive in the contract but separate from "main salary". Maybe only such incentive is modified when a player performs, doesn't perform well or is absent from matches without good reasons. Maybe the salary is basic and guaranteed while the incentive is used to reward/"punish" them for their performance.
This model could work really well in encouraging good performance in other areas of life and it's kind of fair. If I'm an employer, I would offer 60% main/basic salary and 40% incentives in my contract with employees. The incentive will be adjustable, based on their performances