Gratuitous SRN note: Andre Iguodala — DRPM of +2.17, #2 among all guards after Smart and Danny Green — is the Warriors' de facto backup PG, in roughly the same manner as Smart for the Cs.
I note this not just to pimp one of my all-time favorite players, but also to throw Andre's NBA career as a great comp / role model for Smart's likely career path. Like Andre, Marcus will likely remain perennially, criminally underrated by casual fans but duly revered by coaches, teammates, and anyone who looks at numbers that reflect impact on wins and losses more than Fantasy points or all-star appearances.
Like, if Smart ever has to miss a game or three in the playoffs, you guys will rightly point out out how fundamental he is to everything the Cs do at their best, while outsiders will scoff and say, "pshaw, we're talking about a freaking bench role player here — you guys can't win games with three all-stars???"
Edit: for another great Andre/Smart stat, here are the current NBA leaders in AST/TOV ratio, filtered for players who are big/strong enough to guard wings:
1. Iguodala, GS 4.19
2. Satoransky, WAS 3.52
3. Smart, BOS 2.99