Ty Hamilton has never impressed in all of his time on the field. He had one of the worst PFF scores as a rookie, and some of the things I saw in preseason (being completely washed out of plays the vast majority of the time, zero pressure, missed tackles when he had ample opportunities and wasn't washed out of plays) make me question why he was on the roster. As a matter of fact, I see him as the weakest link and easiest cut when AD has to be signed to the active roster. Why on earth would we replace Kobie Turner's minutes with Hamilton and Davis when they clearly are not nearly as good as The Conductor is?
Why did I say "Aaron Donald aside, for obvious reasons"? Because we don't know about his status after the season, if he's going to retire again or not. If he's not at the same level he once was and we win another Super Bowl, he could very well retire right after the season. Not being at his level of play was one of the main reasons he retired. Winning a Super Bowl with Myles Garrett? Sure.
But even then, Kobie Turner currently means more to the defense. Yes, even more than AD. It's not just the sacks. It's not just the stuffs. It's the fact that Turner has - throughout his entire professional career - eaten all of the double teams, the most on the team by far. In half of his snaps last year, he was double-teamed (and that's why Agent Zero feasted). In AD's last year, The Conductor was double-teamed more than AD was.
We have Myles Garrett for two more years after this one, and if Turner takes most of the double teams, more than Garrett, that's more important than sacks alone - because it helps the whole defense. With two offensive lineman double-teaming Turner, edge rushers get less guys on them, less people are required to rush the passer (with four-man rushes), more people in coverage, more potential coverage sacks, picks, incompletions, three-and-outs. More people can be able to stop the run - and Turner has had his fair share of stuffs himself. Turner has still historically gotten home to the QB (nine, eight, and seven sacks through each of his first three seasons, with twenty-seven tackles for a loss).
Add in his major leadership on the defense, and Kobie Turner is the player who is far more important to this team than any other free agent on defense, and any free agent period, Nacua aside, especially since we don't know what AD's status will be at the end of the season.