Only stamina I think.

Edit - also they won't adopt new positions. See Iron Man thread.

ulero wrote: sorry if this question was already somewhere answered, i couldn't find it... anyway: is there any penalty if player plays in both offensive and defensive formations?

i suppose no.
I find some of my players in both formation in first match. they was delpoyed automatically

so... there still is improvement then. That's good to know because my all-stars are best playing on both sides of the ball. I may try to specialize in the future however. I'll try it in my friendly after the first cup game.