Help against 4-3-2-1

[atimforlife]

Sorry for the wrong title, don't know how to change it.

Is this formation legal?
5-1-1-1-2

I'd say no but he has won the last two matches..

i'm assuming it's a flat 5 at the back...
DR-DC-DC-DC-DL
------DMC------
------CM-------
------AMC------
---ST----ST---- ????