4-1-3-2 No MC/L/R

Hi guys, I'm playing against this formation tonight. Just wondering if it's an illegal formation? His formation is:

--------ST--------
AML---AMC---AMR
------------------
-------DMC-------
DL--DC----DC--DR

With no MC/L/R I thought it's an illegal formation but then he hasn't lost a match since, at worst a draw. Though his team is fairly better than everyone in the league (except me).

I'm planning to use the good old 4-4-2 with arrows on MR/ML, attacking both flanks for the first half and Mixed in the second half. Whole pitch, no counter, Zonal, Attacking (My team is fairly better than his).

---------ST-----ST------
-------------------------
ML(UP)--MC--MC--MR(UP)
-------------------------
DL--DC(DW)--DC(DW)--DR

Any suggestions? Is his formation illegal or not? This No MC/L/R is still a mystery... Maybe he only need a DMC/L/R to be illegal?

Thanks,