Let's assume that the Steelers pass on signing Hargrave to another contract since they will have $28m in cap space tied up to just Tuitt & Heyward next year. Very real possibility that Hargrave becomes a casualty because of that, but they will likely extend Heyward to lower his hit.
But again, for the sake of the discussion lets assume Hargrave is gone. Would it be wise to invest a 1st Rd pick on a position DT/NT position that only sees 40% of the total defensive snaps? Maybe... I only say that because the guy they took in this mock is a versatile player that has experience at both DE & DT. Rashard Lawrence could be top 15 caliber by the 2020 draft, so its a stretch to say he would be available to them if the Steelers make the playoffs in 2019. But if so, he's touted as a plug & play D-lineman. If he's as good as they say he is, he could give the Steelers some good options for the future of the D-line. Will Tuitt live up to his contract? If not, they could trade him or cut ties then Lawrence would be their guy. In that scenario it would be easier to sign Hargrave too. Not to mention Heyward is 30 and approaching the tail end of his career.