The "next Troy Polamalu" isn't on this roster -- he doesn't exist. But using him as a measuring stick is unfair, and not wise. The next stud safety may already be on this roster, but if they are compared to Polamalu, they will never measure up.
It's hard to replace a legend.
The reality is that no one on the Steelers' roster now, or in the future, will adequately replace Troy Polamalu, who retired after the 2014 season. He was one a once-in-a-lifetime talent who transcended his position and the game itself.
The good news for guys like Shamarko Thomas is that no one is actually asking them to be the next Troy Polamalu.