You'd probably be hard-pressed to find a player off the bench as important to winning games on both sides of the ball as Smart, but I doubt if he gets any consideration whatsoever.
Generally, high scoring/volume scoring-type combo guards get the nod here, as evidenced by the last ten years worth of winners, which is chock-full of them: Jamal Crawford (3), Lou Williams, J.R. Smith, James Harden (OKC), Lamar Odom (outlier), Jason Terry, Manu Ginobli, Leandro Barbosa, and Mike Miller.