FOXBOROUGH, Mass. — This is no longer about deflated footballs.

Tom Brady signaled in his appeal of his “Deflategate” suspension that he will put NFL Commissioner Roger Goodell’s credibility on trial, further inflating the stakes in what started as a silly little scandal about the air pressure in footballs.

The expected federal court case – and, to borrow a phrase, it’s more probable than not that’s just where it’s headed – could define or limit the powers of the commissioner long after the Super Bowl MVP returns to the field.

“I think this is much bigger than a four-game suspension for Tom Brady,” said Gabe Feldman, a Tulane law professor. “This is part of that continuing battle for the role of the commissioner in disciplinary matters.

“This is a decades-old principal, that the office of the commissioner was created in part to protect the game and to determine what’s in the best interest of the league. This is why (the league) bargained for this back in 2011 – that the commissioner is in the best position to determine that.”

The face of the most successful NFL franchise of this century, Brady was suspended four games after a league investigation found he was “at least generally aware” of a scheme to illegally deflate footballs used in the AFC title game. NFL Executive Vice President Troy Vincent also fined the Patriots $1 million and took away two draft picks.

Brady has denied any impropriety, and the NFL Players Association has appealed the suspension in a letter that demands Goodell recuse himself as hearing officer. Loading the letter with references to NFL decisions that were overturned or otherwise botched, union lawyers laid the groundwork for a court case that would take the decision out of his hands.

“They clearly are teeing up some of the issues that they would be following up on appeal,” said Paul Kelly, former director of the NHL players union.

Here are some of the issues:

THE JUDGE

The collective bargaining agreement gives Goodell the right to hear the appeal, and it also says only the commissioner can punish players for conduct detrimental to the league.

The union is trying to use these two provisions to litigate Goodell into a corner: If he delegates his authority to punish players, it’s invalid; if he does it himself, he is no longer impartial enough to handle the appeal.

The approach held little sway with Goodell, who decided to hear the appeal himself anyway. It might work with a federal judge, but there’s one problem.

“It’s collectively bargained; the players gave that away,” Kelly said. “If they don’t like the results from the upcoming Goodell appeal hearing, they’re pretty well stuck with it.”

THE PRECEDENT

The union seemed to delight in reminding Goodell and the NFL of their recent losses in federal court, including overturned punishments for the Saints in the bounty investigation and in domestic abuse cases against Adrian Peterson and Ray Rice.

But Feldman said Goodell seems to have avoided some of those mistakes in Deflategate. By delegating the probe to Wells and the punishment to Troy Vincent, Goodell may have preserved his independence sufficiently to preside over the appeal.

“The NFL has clearly learned from all of the cases that have come before that … to protect the decision if it comes to federal court,” Feldman said. “I think the NFL made a clear effort here to remove that conflict.”

Kelly wasn’t convinced. Even though different people made the decisions, he said, it’s not clear they were independent.

“Goodell hires Ted Wells and his firm, pays them an exorbitant sum, supports publicly Troy Vincent’s finding and sanction and now is going be the final arbiter of the matter, unless the court gets involved,” he said. “There isn’t a truly objective fact-finder.”

THE FACTS

In many ways, though, the hearing in front of Goodell is Brady’s best shot.

The commissioner can take a fresh look at the evidence and, if he wants, reject the conclusions in the Wells Report. He can ask for new information and consider it as well.

“The commissioner is certainly not bound by those findings,” Feldman said. “But the NFL has to provide the players with the rights that they bargained for.”