
18. Joe Montana
This wasn’t a blockbuster trade in terms of the outlay. But we’re talking about Montana leaving San Francisco so of course it was massive. Steve Young usurped Montana as the 49ers’ starter after the latter’s injury. He didn’t want to be a backup for the remainder of his career. That’s why he forced the franchise into choosing between him and Young (via Kansas City).

In the end, the 49ers went with the younger man. They traded him to Kansas City in exchange for a couple of draft picks. Montana was decent for the Chiefs as helped them to a couple of postseason appearances. It was strange to see him playing for another franchise like when Tom Brady joined the Bucs. Some players have such a strong association with a team that it’s shocking when they move.