This article by Sarris and Ghiroli in _The Athletic_ covers baseball only, but the same question arises for all of the major sports. With the explosion of new data available, who does the data belong to: who gets to use it, and when?
Knowledge is power; when team officials sit down to negotiate with a player's agent, there will always be some information asymmetries, information that one side knows that the other side doesn't. But the new data -- and equally importantly, analysis of said data -- might alter those asymmetries in important ways. Or maybe not, if agreement can be reached about who owns the data.
The article made me realize that professional sports have long operated under an unusual data ownership scheme. Forget about newfangled stats, for decades or even over a century a player's health data has been a vital piece of information. Normally a patient's data is protected by HIPAA, a powerful data privacy law. But players are inspected by team physicians not (or in addition to) their private physicians. In the bad old days a player might simply follow the advice of the team physician but I think those days ended probably around the time of Bill Walton. Teams still can use their physicians to monitor players' health -- but do they get to withhold information from the player? Or have collective bargaining agreements forced them to share their findings with the player and the player's physician?
The new tracking and performance data open new fields of data; have the collective bargaining agreements started to address them? What data must be shared, and what data can be withheld?