Let's take a look at how the balloon sweep works after the jump.
First, the balloon sweep is an open guard sweep against a standing opponent. The intent is to get off your own back from underneath your opponent by reversing your opponent and ideally, securing yourself full mount.
To perform the move, while on your back in open guard, place both of your feet on your opponent's hip and grip each of your opponent's wrists with your respective opposite hand. Pull your knees in to lift your opponent off his feet until his eye level above yours. To make the flip easier, you can also push your opponent forward with your feet to bait them into driving towards you, giving you added momentum to take them over. Guiding your opponents arms with wrist control, back shoulder roll as you continue lifting your opponent with your feet until your opponent floats over you and onto his own back. In a controlled setting, by back-rolling you should be able to land directly into full mount.
At UFC 121, Sanchez was aggressively punching from inside the open guard of Thiago. Sanchez had his right knee down and his left leg up. Thiago timed the moment Sanchez raised his right knee to stand up and as soon as Sanchez stood up, Thiago quickly placed both his feet on Sanchez's hip and pulled down with both hands on the back of Sanchez's head to flip him over (Please note: In Thiago's case, instead of controlling his opponent's wrists, he pulled Sanchez's head down to flip him over, which is also correct). Also, the push-pull technique wasn't needed here as Sanchez was already leaning forward from being so aggressive. During the sequence, Thiago actually flipped Sanchez so far back that Thiago wasn't able to back-roll into full mount and was put into a scrambling position.
The balloon sweep was a neat move pulled off by Thiago late in the second round, but unfortunately, would be overshadowed seconds later when Sanchez scrambled to secure a double leg to lift Thiago up for a running powerslam.
Thiago lost the fight to Sanchez by unanimous decision after three rounds.