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Jim Brown is happily enjoying his crow today ... 'cause the Browns legend tells TMZ Sports he was so wrong about Baker Mayfield -- he actually thinks Cleveland's got a shot at the playoffs now!!

You'll remember ... Jim was one of the least pleased people in Cleveland when his ex-squad chose Baker over Saquon Barkley with the top pick in the NFL draft.

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But, after watching Baker's 21-17 comeback performance against the Jets last week ... he's all in on the selection now ... even apologizing to John Dorsey and co.!!!

"They didn't go with what everybody said, including myself," Jim tells us.

"They went with what they thought was correct, and I really appreciate being able to say to them, 'I guess you were right.'"