Some times good players go bad too.

Power Training is high 'cost' and not something to be done with a poorly performing player unless he has been good in the past, imo.

If a player trains fast enough a bit of training to tweak the bal;ance of his stats might be worth a try - but only if he seems worth the effort.

Normally, I'd start by looking at the position he plays and whether my orders are contributing to his bad form.