User blog comment:Kaido King of the Beasts/Chapter 879: Mirror Battle in Mirro-World/@comment-27930128-20170922112820/@comment-71.13.82.131-20170922193837

Gear 4th seems like a bad idea right now for Luffy to learn during. If Katakuri can counter in any way then Luffy will just be worn to exhaustion, which will result in him being easily defeated. Luffy will need to find another option than Gear 4th right now, so hopefully Katakuri starts to do his own offense before they would just to that. Luffy also has no where to run in this world, without Brulee to let him out.