man, that is not a reasonable way to think. kakashi and sasuke are not weak physically (if you meant physically = taijutsu). kakashi is probably the most well-rounded ninja we've seen so far. just because gai is weak in nin/genjutsus that doesn't mean necessarily kakashi will be weak in taijutsu. that logic can't be applied on everyone cuz there are only a few characters who are only one-dimensional (jutsu-wise) and majority of the characters are more well-rounded.