Training a Special Ability or New Position

[Rautz]

it affects the performance

I've seen this advice in a few places: 'don't train before the game, do it after'

As a multiplayer online game it doesn't make much sense to me.
Some people(me included) have the matches set at the end of the day, they can only train before.

Also I interpret their official post the same way:

Also remember that your players will have a worse performance if they play a match tired, so don’t train close to the start of a match unless you have the Rest Health Packs to make up for it.

Emphasys on UNLESS.
Their advice is not about training before the matches, but about having low condition at the start of the match, and thinking about that when training.
The word unless means that if you do regenarate your condition with packs it doesn't affect performance. So the most important thing is to have you player condition high at the start of the match, no matter the way it got that way.