The Notts boss claimed that Alan Hardy, having taken over the club a month ago, was not happy with the clause, given the club's risky situation near the bottom of League Two, but they would review his deal "as soon as we're safe".
Nolan told the Nottingham Post: "When I first came in he had to make one more appearance and he would've got a new contract.
"But the chairman wasn't happy with that, so we spoke to Duffer and said 'if you take the clause out you can be available to play'.
"He said 'take it out, I don't care, I want to play for this club' – and fair play to him, hats off to him, the man has been absolutely fantastic since I've walked through the door.
"The fans should know what he's done because he wants to play here, he wants to do the business here.
"I've seen a lot of players down the years when they've got it, going 'no I'll just sit here and take my money'.
"But that's not Richard Duffy, he wants to be involved, he wants to help the cause.
"And he knows if he keeps performing the way he is there's going to be people wanting to sign him at the end of the season, and hopefully it's going to be us who gets him.
"I've said to him, 'as soon as we're safe, we'll talk'.
"Hopefully we will get safe as soon as possible and then we can start talking contracts with lads who we want to keep.
"Listen, that's way down the line. All I want to do is put it out there what that lad's done, and how much he's here for the cause.
"When you've got people like him in your dressing room you've always got a good chance."
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