Which, in turn, might mean drafting a T a round or round and a half later, giving them the latitude to take a different player at some other position of need.
This close to the draft, there are no insignificant roster additions. They all affect the draft to some degree. Gute didn't just grab 'im up because after 2 months he finally decided the guy's a bargain; he's looking at draft charts every waking moment and seeing them in his sleep at this point. He has a rough list of roster spots he wants filled or strengthened. He signed Dillard because he feels Dillard meets a need, and now that's a need that doesn't need to be filled in the draft.
Even if it only frees up a 6th round pick, it's still something of value to Gute in the draft - even if only trade currency to move up in an earlier round.