NFL great Joe Montana said he thinks the New England Patriots “made a mistake” allowing Tom Brady to walk away and sign with the Tampa Bay Buccaneers after 20 years.

The former San Francisco 49ers quarterback, who brought the franchise four Super Bowl championships, told USA Today on Wednesday that he just doesn’t understand the Patriots' decision to let their best asset go.

TOM BRADY MADE DECISION TO LEAVE PATRIOTS ON NIGHT OF ROBERT KRAFT MEETING

"I don't know what's going on inside there, but somebody made a mistake," Montana said.

“I think when you look at the whole situation, you try to figure out how you want to get away from things that are there. I had a different story, where they had made a decision. He, obviously, they never would have gotten rid of. I still don't understand how New England let him get away. I don't understand that."

Montana, who left the 49ers to join the Kansas City Chiefs at the tail end of his career, said the motivation to leave might have been Brady’s desire to win another Super Bowl which would only be achievable with more “weapons,” something the Buccaneers were able to offer.

“I don’t know exactly what he’s looking for, but my understanding was that he’s just looking for more control of the offense,” he said. “But more weapons doesn’t always mean you’re going to continue to win. There were times we had a lot of weapons later in my career, but we had up and down years.”

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Montana said the “pressure” to perform will definitely be a factor next season, but that the challenge will be something good for the six-time Super Bowl champion.

“Probably for the first time in a long time he’ll be having fun if I understand what he’s been saying, or what I’ve been reading.”