I think it would be very hard for Schiano to successfully sue for defamation. he is a public figure, and a public figure must show not only that a false statement was made, but that the false statement was made in "reckless disregard" of the truth. To have reckless disregard, the declarant does not have to know that his statement was false, but it's not sufficient for the misstatement to be the result of negligence. This kind of showing is just so hard to show. In addition, statements of opinion, no matter how outrageous, cannot be the basis of a libel suit. To add to that, truth is a defense in a defamation case, and so, as mentioned above, the pretrial discovery could delve into what Schiano may have known. And I should add that litigation would be extremely expensive and Schiano would probably have to pay out of his own pocket.
In other words, I think it is unlikely that he has any recourse. The fact that the material quoted out of McQueary's deposition is hearsay would be helpful to Schiano, but the question isn't whether the statements by his detractors were based on hearsay, but rather whether they were both false and published in reckless disregard for the truth.