Yes may element talaga ng luck. Cousins is the perfect example. He was on a contract year when he got injured. What should have been a massive payday for him turned out to be a series of vet minimum contracts due to his ACL and Achilles injury. Till now he is trying to prove that he can be a productive player. Same case with Isiah Thomas. Injury on a contract year greatly diminished his value.
Meron din naman na nakuha nila yung max contract before they got injured. John Wall, Klay Thompson, Gilbert Arena are all examples of that situation.
The other case is being undervalued is when you join a superstar team and you are not featured as the primary option. Kevin Love is one. Prior to joining the Cavs, he was the franchise guy for Minnesota. Sa Cavs he was the third option. Same case with Chris Bosh when he joined Miami. Love eventually got paid the max contract and was once again featured as the star player when LBJ left the Cavs. Chris Bosh as well got paid when LBJ left Miami but unfortunately after he got the contract his career ended prematurely with an injury (blood clot)