Don't think they can technically do that until after the draft (or at least after the first round) tangentially, a team like the falcons could negotiate and not sign him until after the draft. Use a top ten pick, count on Lamar to get them to the playoffs and trade much later picks in 2024 and 2025. Of course there is a risk that the ravens would match
Edit: I am sure they can't sign him until after the draft. I don't know about actually negotiating.