Everything to stop injuries includes higher physical stats, upgrading pitch and facilities, not playing hard anything, using the option to train individually to not go below where they will recover for the next match (and stay green! you can train just don't push them to below about 80%)

The amount of Tokens or boosters doesn't seem to correlate to injuries.

Most injuries for me happen early & late in Season.

This Season I think I will record all my injuries in a thread to see how bad it is.