Rosters in the NHL aren’t constructed by looking at each player in isolation. You have to have fit — cost, cap hit, term, role, age, and a lot of other things as well. And the less cap wiggle room a team has, the less you can just zero in on one player.
But at the same time, you do only negotiate one contract at a time, and for all GMs have tried to handle multiple expiring contracts by trying to play one off against the other in the press — the agents only care about one player at a time.