Quote Originally Posted by LOS ABRANTES FC View Post

I mean a single drill that trains GK skills and outfield players .
Hm, you mean like if a drill you use covers things like Rushing out and/or Communication and other attributes that exist in in non-GK skills? In that case, everything is fine.
As long as a player has attribute(s) that a drill covers, he will be able to receive gains, while expending his Condition stat.

EDIT: Example - If you use the drills "Fast Counter-Attacks", "Video Analysis", "Hold the Lime", which all cover the Communication attribute and then you add outfield players with the proper Defence and Attack attributes AND add a Goalkeeper, everyone will expend condition for these three drills, and the ones who have the appropriate attributes can gain an increase to said attributes, including the GK because Communication is a goalkeeping attribute, and is present in the drills that I listed.

Note: Just in case you mean something about mixing drills that cover different skills - No penalty. Nothing bad. Doesn't even matter if you have a GK drill in there, it will cost Condition and if there's a GK to benefit from the drill, he will. That's all.