Joe Montana and Steve Young
Amazingly, the Niners had the fortune to go from Montana to Young. The two men are Hall of Famers and up there with the greatest quarterbacks in NFL history. But they were bitter enemies during their football careers because Young took everything Montana worked for. Ultimately, San Francisco decided that Young was the future after Montana’s injury woes.

However, Montana resented the Niners because he felt that they always wanted to replace him. He resented Young’s success and forced an exit to the Kansas City Chiefs. Later, Montana acknowledged that he doesn’t have bad feelings toward Young now. His replacement found himself between a rock and a hard place (via Sports Illustrated).