Chelsea boss Antonio Conte admits his players displayed a "bad attitude" in defeat to Arsenal.
And he says a change of system is now likely.
Conte told BBC Sport: “It was a bad performance, the worst in all the games we have played up till now. From the first minute we had a bad attitude. I think it's important to understand we must work a lot to improve.
“Will I consider 3-5-2? Yes. Now I have to consider everything because I have to find the right balance. It's the right moment to consider all [systems] to improve the situation because in every game we are conceding two goals. This is incredible and we are following [what happened] last season. We must show we want to fight for something, otherwise we will lose a lot."