I believe there was one year back in the late 2000s in which the Pittsburgh Steelers were able to return 21 out of 22 starters from the previous season, or something like that. That is an extreme rarity, and certainly won’t be the case for the team as they transition into the 2021 season.
They have already had two players retire in Maurkice Pouncey at center, a starter, and Vance McDonald, who served as their blocking tight end. Alejandro Villanueva, JuJu Smith-Schuster, Bud Dupree, and others are shoe-ins to leave in free agency. The team will look a lot different.