well, i think the friendly game is just to test your formation) also the player fit in that formation, I don't thank that really affect to regular match... but usually...i only use the bench for friendly games since i don't use them a lot..but still need to keep them fit to match.... while my 1st team will save for the important games...well... if in the friendly game...your player is not perform well...you better put your sub in right away and let the one who is not perform well to have a rest... usually... i against to the lowest team... and in the half time...anyone who's rating is not over 7...i put sub in....and better to stick to same formation...case they might play differently even they can play different role...(like my ST... he can play AMR too... i play him in ST most of the time...when i put him in AMR...so far... he won't score or have any assist =.=... in ST, he score some and does many assist (and yes...he is ST -.-) )