What happens if you’re playing with 9 and someone gets a red card?

I urgently need to lose a league match because I don’t want to get promoted (my team just isn’t good enough right now).

I’m planning to play with 9 players, but… what happens if someone gets red card and I’m down to 8 on the field? Would I lose the training?

My opponent also wants to lose. Wouldn’t it be enough to just play my guys out of position? If I go with 10 or 11 players, I might actually end up winning