Ngannou last year put his MMA career on hold to make a switch to boxing, where he faced Fury in October.
The ex-UFC champion scored a shock knockdown and was beaten only via controversial split-decision.
Ngannou now fights Joshua on March 8 in Saudi Arabia and British boxing legend Hatton admits there a still several questions left to be answered.
He told Instant Casino: “We’re in limbo aren’t we – was Ngannou better than we gave him credit for, or did Tyson take Ngannou lightly?
“Did Tyson not train as hard as he could and that’s why Ngannou looked as good as he did?
“There’s a big question mark around Ngannou, we all know he can hit, but was it because Tyson took him lightly?
“All these questions no one is sure about yet. Tyson didn’t physically look as good as he normally does.
“And he’s also had those three fights with Wilder that may have taken something out of him.”
Fury, 35, was due to face Oleksandr Usyk, 37, for the undisputed title on February 17 but a cut sustained in sparring has moved it to May 18.
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So Ngannou, 37, looked elsewhere after being denied a rematch and instead struck a deal to fight Joshua, 34.
Despite the MMA star’s impressive performance over Fury, still Hatton is tipping AJ to get the job done.
He said: “If you’re asking where my money would go, it would go on AJ because he’s an exceptional boxer, you don’t become an Olympic gold medalist and a two time world champion for nothing.
“He doesn’t have the lateral movement of Tyson Fury, so he’s going to be standing in front of Francis Ngannou, which worries me a little bit because if AJ does cop one, that could be that.
“But I’m going to go with AJ based on his confidence and his new team. I think he’ll have enough firepower to shine against Ngannou.”