User blog comment:FairyRaven/Fairy Tail Chapter 427: Pitched Underground Battle, Review and Commentary/@comment-5303512-20150412134013/@comment-7418318-20150413054003

That's not what I meant.

At the beginning of the fight Yuka was talking and Natsu let loose a blast at both him and Tobi, which knocked Tobi on his back, seemingly KO, while Yuka blocked it with his wave magic.

Tobi got back up after this seeming one-hit KO, then came the fight Natsu vs. Yuka and only then did Tobi fight Natsu and knock himself out.