User blog comment:AYET/Let's Discuss Chapter 733/@comment-1595565-20131226053307/@comment-13876472-20131226164205

You pretty much summed up the investigation DP. Oda's scetces here are clearly "keeping distance" for what we have seen and evolves Conqueror's Haki. Most of all I doubt it is Haki, because of the blunt traumas that are not shown in any previous panel. Although Sabo's line could fit perfectly for a Haki incident.

As for what the cause could be, if we are speaking about a technique the more similar thing comes to my mind is Kuro's Shakushi. It would make sense to see an upgraded version of the fastest technique revealed so far and can also explain why the user felt to the ground.