Performance based compensation

In some professions, it is a must that compensation is based on how you perform, but contract or no contract, I cannot understand how is sports or in any field where there are contracts does the signers draft something in the contract that if you reach certain level of performance than you will get the full compensation. The most glaring example I see is in the sports industry where you are injured (not by their fault), not feeling well or not performing the minimum, you still get paid the full amount of your contract even if you are not playing all year long. In most industries you work all year long and then you get a paltry amount not commensurate with your performance and you are happy that at least you have a job but not in sports or for that matter movies also. Although I believe that as you keep on making bad movies you are not paid that well but still my main focus is in sports. Now as usual not many people will agree with me since they are sports fanatic but think about it in a neutral way. You are paying a guy to play with millions of dollars of not clubs money but with people’s money and then you underperform and still get paid no matter what because it says in the contract. I don’t believe it is fair since the common folk is struggling to just get by after working their back off and then there are these guys who are enjoying all the perks including what they love to do and you don’t see that kind of performance to match their salaries. I mean is it really fair?