How do long-term-injured reserve (LTIR) work?
Teams receive cap relief when a player is considered to have a "bona-fide long-term injury" — injuries that cause a player to miss at least 10 games or 24 days. This is one of the most commonly misunderstood aspects of the CBA.
Just because a player is on LTIR does not automatically grant the team extra cap space. In the event a player is placed on LTIR, his cap hit still counts toward the team's overall cap payroll. Relief only comes if replacing the player's salary pushes the team's cap payroll to date over the cap. The amount of relief is limited to the amount the team has gone over the cap (less the amount of payroll room the team had at the time the LTIR transaction took place), not the entire amount of the injured player's salary.
There is no formal designation of "replacement players."