"I'm afraid to mention anything because I'm not sure of the rights things and contract issues down there. We'll leave that up to (Seahawks general manager) John (Schneider) to figure out."
Carroll said he did not meet Hayne when the 26-year-old visited the Seahawks' facilities last month after meeting University of Washington coach Chris Peterson.
Pressed about Hayne, Carroll said: "I don't think I'm able to talk about that.
"We couldn't talk about a player on another (NFL) team, so I don't want to mess it up. But it's a pretty exciting thought.
"I've always thought it would be cool to recruit down (in Australia) and all that because there are some great players and it (rugby league) is a great game.
"It's a very physical and demanding game, so those guys have all the same stuff we're looking for in our guys."
Carroll was then asked about rugby league players in general.
"They're great athletes," Carroll said. "They run fast and they hit hard. The style of throwing and catching is different.
"I'm sure our guys could cross over, too, once they figured out how to lateral and kick it on the run. Well, we'd be miserable at that, I'm sure. But there's a lot of general carry over because of running and tackling and making people miss."
So could a rugby league star make it in the NFL?
"I think it would be really hard and a tremendous challenge," Carroll said.
"Only a certain few could do it. There would need to be a lot of patience from the (team). I don't think a guy could come in in the middle of a season. I think it would take more time than that. But we've seen guys over the years who have made the transition from other sports."
Reporters also asked Seahawks cornerback Richard Sherman if Hayne could do it.
"It depends on what position he is trying to play," Sherman said.
"If he can adjust and grasp the strategic part of the game, I think he would do fine. That's to be seen."
