Kenpachi not inflicting a single wound off is lame as hell considering how severely he beat down everyone else he came across, but him winning was not going to happen by any means.
Ofcourse, it smart story wise on the author's part to get him out of the way as soon as possible along with the commander. This group is centered around disabling bankais and with the commander and kenpachi being the strongest captains both in strength and high reiatsu, theyve never had to resort to using a bankai to dispose of their enemy, quite upper hand, to draw this story out and make it more dramatic for us, getting them out of the way asap lengthens the story.
The author has done his part to keep these key power houses under wraps most times to allow ichigo to keep his "saving the day" card. They are never around during critical moments or for some reason the author has made some kind of plot( WW special ability) to stall a fast victory. Same can be said about urahara/Youichi/Unohana(rumored to be one of the stronger captains) they are never in the fights or around, the author does a very good or bad(depends how you see it) to show who his strong characters are and limit their "show time" during the story.
Kenpachi still has his clothes on which tells me he was either caught of guard by something or he did not have the chance to go full out, kenpachi likes to draw out fights and this probably was not one he had that chance to and missed his opportunity to rebound from that error. Im only hoping he still has his eye patch on, or "thinking" as he did with Nnoitra.
I await in anticipation with what the commander will do considering he cant bankai and only has 1 arm to fight with.