For reals, that's an unneutered tomcat, the heavy shoulders and huge head are dead giveaways. The size of him and the prominence of his cheeks and jaws suggests he's middle aged or so in cat years. Got some years on him at any rate. Likely the king of a cat colony that works the stadium and the area around it. Probably disturbed out of his hiding place when someone needed some equipment.
Probably a permanent resident of the stadium who, along with his females, makes a living keeping the rodent populations down and collecting scraps here and there. Most stadium crews won't disturb local resident cats because they provide a service, but usually they manage to stay out of sight during a game. I guess it chose the wrong equipment locker to hide under this time.
Looks pretty well fed, I'd bet some of the stadium crew look after it and other resident cats, again with an eye towards keeping the rats humble. New Jersey rats take some humbling after all.