Are you talking about negotiations or arbitration? In arbitration:
Admissible
- The number of games played and a player's injury history
- "Overall performance" (including NHL "official statistics")
- Length of service of the player to the club or in the NHL
- "The overall contribution of the Player to the competitive success or failure of his club in the preceding season"
- "Any special qualities of leadership or public appeal"
- The overall performance of alleged comparable players
- The compensation of any comparable players that have been formally introduced as a comparable
Inadmissible:
- A contract entered into when "the Player" was not a "group 2" restricted free agent
- Any contract signed by an unrestricted free agent (so only group 2 restricted free agents can serve as comparable players)
- A contract signed by a player that is not being offered as a comparable player
- Qualifying offers
- Prior negotiating history between the club and the player
- "Testimonials, videotapes, newspaper columns, press game reports
or similar materials"
- Any reference to walk-away rights
- Any arbitration award that a club walked away from
- "The financial condition of the club or the league"
- References to the club's salary cap situation, or the players' share (of hockey related revenue)
- Any arbitration award issued in 2005-06, or any reference to a salary arbitration opinion that took place prior to the beginning of the salary cap era
In 2020 the NHL and NHLPA agreed that comparable players must be as close as possible in age, position and TOI. They also changed "Any arbitration award that a club walked away from" to "Any arbitration award".
Each side submits (a maximum) 45 page argument to the arbitrator as well as exchanging them between the two parties. You really think that if one side brings up a player as a comparable that is not allowed, the other side is going to allow it? If you do, I have some swampland in Shakespeare for you. It's a quick drive for you!