Key combination for battle with Classic Smoke (Mortal Kombat (2011))

As you know, in the mode of stairs there are secret battles with classic characters - Jade, Reptile, Noob and Smoke. To battle the latter, you need to wait for it to look out from behind the tree and during this time click Down'Select (on PS) or Down 'Back (on XboX). Unfortunately, the combination for the computer is not written anywhere. Does anyone know what buttons you need to press to join the Battle with Smoke?