One of Buzbee's allegations is that the Texans failed to prevent Watson’s ongoing misconduct, once the team knew or should have known that he was engaged in questionable behavior. That's basically a claim of negligent supervision. This is a simple negligence causes of action based on an employer's direct negligence rather than on vicarious liability (which Buzbee is also alleging but is much more difficult to prove).
To impose liability on an employer under the theory of negligent supervision, a plaintiff must show that an employer's failure to supervise its employees caused his injuries. The harm imposed on the plaintiff must still have been foreseeable by the Texans, and the harm must have still been employment related (basically were the massages somehow employment related). Like any negligence claim, it has to be shown that the Texans owed these women a legal duty (that includes that the Texans should have foreseen the risk of what Watson allegedly was doing), breached that legal duty, and the plaintiffs suffered damages.
So yes, even if no contract between these women and the Texans, it can still be considered a potential workplace issue and the Texans could be held liable. I'm not saying it is likely they will be held, but the claim could survive a motion for summary judgment.