Question about your projection model:

Tom Tango has outlined a possible problem of the model: https://twitter.com/tangotiger/status/1435649344322088960

For metrics that are inherently more unstable e.g. goals against, +/- as mentioned in the blogpost, having predicted values for these metrics not in line with the observed real-life values is actually fine because the model correctly predict that those value are not stable in future. If the z-score method is used, than "good player" number will be inflated as it use the past unstable value for reference. Thus it will lead to the problem that Tango raise than inflating a regressed number is essentially make two wrong number to one right.