My reading of the Preuss situation is thus:
Max Gawn is Melbourne’s #1 ruckman. He is contracted until the end of 2021 at which time he will be 30 years old. Many factors will determine what happens with Max at the end of 2021 but you might assume he will get another contract that takes into account how many more years his body can handle rucking and whether we have a spot for him to rest forward etc.
Braydon Preuss is Melbourne’s #2 ruckman. He is contracted until 2021 at which time he will be approximately 26 years old. Many factors will determine what happens with Braydon at the end of 2021 but you might assume that he would now have 3 years of training with and learning from the premier ruckman in the AFL under his belt. If he has learned well from Max he might get another contract with Melbourne. Or he will be able to seek a trade to another club that needs a ruckman (and there is always one or two that do), and he will probably do well out of it having done his apprenticeship under Max and at 26 will still have a few years of football left to make his own mark.
I’m thinking there is a long term approach to this with both Melbourne and Preuss benefiting.
We get a backup ruck for the next 3 years and at the end we either have a ruck to take over from Max or an easily tradeable ruck commodity.
If he gets a few senior games rucking or in the forward line in the meantime then that’s a plus for him.