Meh, I think this race was Toss-up or Lean D with or without Coakley.
Yeah, not having Coakley wouldn't make this Safe D. According to hypothetical polling, the democrats having Berwick, Kayeem, or Avellone as their nominee would have actually made this a Likely R race. With everyone else, it'd be a tossup, or at the low end of Lean D/Lean R. The only democrat that looks they would have defeated Baker easily would be (congressman) Joseph P. Kennedy II.
MA is purple-blue when it comes to gubernatorial elections. Democrats have their huge registration advantage, but the right sort of republican can still do quite well.