Carroll said he talked to Lynch, who retired from the NFL and Seahawks after the 2015 season, about 10 days ago.
"He came through the office and had a good visit," Carroll told reporters at the NFL meetings in Phoenix. "I know that he is somewhat entertaining the thought of it. I can't tell you how strong it is. You've got to talk to him. And that chance isn't happening."
ESPN and NFL Network reported earlier this month that the Oakland Raiders would be interested in Lynch should he decide to make a comeback and come out of retirement.
Lynch's playing rights are owned by the Seahawks as he has two years remaining on his contract. He has been on the reserve/retired list since May 2016.
Carroll was asked if Lynch could play for the Seahawks again, but the coach responded, "He's retired."
Lynch would be due a salary and cap hit of $9 million in 2017, and he would be in line for a base salary of $7 million in 2018, along with a $3 million roster bonus, according to ESPN.
Lynch turns 31 on April 22, and Carroll admitted he is not sure whether the running back could still be effective.
"I don't know," Carroll said. "It depends on how he's approached this offseason. He looked OK. The mentality that it takes to play this game the way he plays this game, he has to really be invested and ready because he goes deep when he plays. Whether or not that's still in him, the burn is still there, I couldn't tell that from talking to him. I know that he was playing with the idea."
There is no indication the Raiders have contacted the Seahawks yet about Beast Mode. Seahawks general manager John Schneider and Raiders GM Reggie McKenzie worked together in the Green Bay Packers' front office.
Schneider told reporters at the NFL meetings on Tuesday that nothing has changed in Lynch's status as a retired player.
"I talk to his representatives all the time," Schneider said. "They have a ton of players. Marshawn, what I can tell you is he's on reserve/retired as a Seattle Seahawk right now. And that's where it stands. It kind of took off like wildfire for one weekend."
If he stays retired, Lynch will finish his nine-year NFL career with 9,112 rushing yards and 74 touchdowns in 127 games, and another 1,979 receiving yards and nine TDs.
Lynch has repeatedly said he has no intentions of returning to the NFL, even for his hometown team in Oakland. On Monday, NFL team owners voted 31-1 to approve the Raiders' application to relocate to Las Vegas, likely starting for the 2020 season when the new stadium is finished.
"I'm retired. Is that good enough? Which camera do you want me to look into? This one? I'm done. I'm not playing football anymore," Lynch said last June in a "60 Minutes Sports" appearance on Showtime.