Ospreys were reduced to 14 men against Leinster when lock, Ian Evans, was sent off for use of the boot on Mike McCarthy's head.
McCarthy was laying on the ground under a maul at the time. After Romain Poite consulted with the TMO, he deemed the offence to be worthy of a red card.
You can clearly see Evans (number 5) repeatedly using the boot on McCarthy's head in the GIF below.
As you can see, McCarthy was left seriously bloodied.