the NCAA, the specific school, the conference, the bat manufacturer, the umpire, the people in the stands.
If you can make a case for negligence, anything a player signed is basically worthless. And everyone from bat manufacturers to the NCAA and everyone in between can be named.
I order to file a lawsuit you must have standing to do so. And I am pretty sure the one person who does will not be doing so. If there ever was a lawsuit I would look for it in High School where a proof of negligence would be much easier hurdle.