1-2-5-1-1... How is this not an illegal formation?

So I got destroyed by a guy playing a formation with 1 defender...
His formation was a 1-2W-5-1-1. Yes you read that correctly, he used: DC | DML - DMR | LM - CM - CM - CM - RM | AMC | ST.
This is such a weird formation, I'm not even sure how to begin to play against it. I'd assume either try to either stack the midfield or defence and hit him on the count with long passing... so I tried a 3N-2N-3W-1-1. But it didn't work last time, we are about equal worth skill point ratings, but my team is worth almost twice as much as his.
Any suggestions?

The DM's now count as D I think in terms of illegal possession, that counts as ok.. weird as heck though.

I would play hard defending with counters in whatever your best defensive formation is, mine happens to be 4-2dmc-1-2W-1.

Thanks, I was just so thrown off by it, didn't take it seriously. I'll try your recommendation in the next match.