User blog comment:Xilinoc/Ch. 562 - THE VILLAIN 2 (Mask De Masculine is a Mexican luchador in a German army)/@comment-6963992-20131218213812/@comment-11051098-20131218232324

Out of the logic in your last line, Renji shouldn't know enough about Mask either, to be able to defeat him. But, he could have been nearby after he and Rukia arrived, close enough to pick it up when Mask revealed how his power works, after he took out the 2 captains the first time.