The NFL has threatened four players, including Steelers linebacker James Harrison, with suspensions if they don't they don't cooperate with the league's investigation into allegations that they all received performance-enhancing drugs from the Guyer Institute in Indiana.

Last month, Harrison said in an affidavit sent to the NFL by the NFL Players Association that he never violated the league's policy on performance-enhancing drugs, nor has he met the man who alleged to Al Jazeera America that he supplied Harrison with an illegal substance. Harrison has said previously that NFL commissioner Roger Goodell will have to come to his house to interview him, adding that the league must show "credible evidence that warrants an interview."

He extended the invitation again on Tuesday.

"I don't have a problem doing the interview. Come to my house. Bring Roger (Goodell) with you," Harrison said, via

But here's the thing: The league doesn't have to show "credible evidence." That's due in part to the collective bargaining agreement, on which the players signed off before the 2011 season.

And now, Harrison is between a rock and a hard place; he can submit to the interview, but that will set a dangerous precedent, as's Kevin Seifert eloquently describes. "If someone, anyone, makes a public allegation, substantiated or otherwise, recanted or supported, of possible improper conduct, the player must submit to an investigation on the league's terms or face suspension," Seifert writes.

Or Harrison can refuse to be interviewed and be suspended indefinitely.

"If that's the case, then somebody could come out and say James Harrison is a pedophile," Harrison said in response to a question about why he doesn't get the interview over with if he has nothing to hide. "They are going to suspend me, put me under investigation for being a pedophile just because somebody said it? I'm not going to answer questions for every little thing some Tom, Dick and Harry comes up with."

So is the 38-year-old linebacker prepared to sit out?

"Definitely," he said, adding, "I'll do what I have to do. They'll do what they have to do. We'll make that decision when that time comes. ... I just am doing what I'm advised to do (by the NFLPA). It's the right thing to do."

Steelers coach Mike Tomlin said that he isn't advising Harrison, though Harrison concedes that the team could factor into his decision.

"I'm sure it would lean me in that direction because I don't want to let my teammates down," Harrison said. "I don't want to let the organization down. We'll deal with that when the time comes."

Charlie Sly is the source for the Al Jazeera America report that implicated Harrison and three other active players -- Packers linebackers Clay Matthews and Julius Peppers, and free agent Mike Neal -- as well as recently retired Peyton Manning. Sly since recanted his account -- and Al Jazeera America has gone out of business -- and because of that, the NFLPA argues that the players shouldn't have to discuss the matter with the league.

The league, obviously, doesn't agree.