Hi Gabez, long time to see you.
My opinion (to make things more sinmple)
a weaker (in all skills , not only in speed) defender would have a disadvantage playing m-m vs a good, fast attacker but as TE is a game and not real football, I would guess that m-m can be also or more effective as it gives a penalty in codition loss, so I believe it gives a + in his defensive actions.
But all those are just theories as only devs know the truth and none of us can get a solid conclusion from the games.
There are too many factors and different conditions in every match.