http://www.ign.com/articles/2014/10/24/wwe-2k15-who-got-nxt-mode-announced-and-detailed

A brand new game mode for WWE 2K15, called Who Got NXT, was announced today by 2K. The new mode will be exclusive to the last-gen versions of the game.

Who Got NXT centers around NXT superstars Sami Zayn, Adrian Neville, Rusev, Corey Graves and Bo Dallas. Each of the five wrestlers has their own chapter, which consists of four matches. Completing these matches in order, along with each match's stipulations, will unlock each wrestler on the main game's roster.

Completing all five chapters of Who Got NXT will unlock the Proving Ground mode. Proving Ground is described as the spiritual successor to WWE 2K14's Defeat the Streak game mode. While Defeat the Streak pitted players against Undertaker, Proving Ground will put you up against WWE 2K15 cover star John Cena.