for unknown reason I always find difficulties in cup matches!

Today an unexpected draw against a very weaker team playing home.
I wonder how it's possible that a 12 skills players could stop every time a 33 skills players!
But well, nothing it's compromised!
We must win away hope for a bit more luck!

I keep winning in league 6 - 0 minimun.
Is there something special in cup that I have to know?