That's correct, but there is no "KEY GUY".
You can have a triple-crown winner and not win the WS. The Sox have done it. (Yaz & Williams 2x).
You can have the Cy Young award winner and not win the WS. The Sox have done it.(Pedro, Porcillo, Clemens 3x) You can have the MVP and not win the WS. The Sox have done it,. (Pedroia, Rice, Clemens, Vaughn).
There is no "key guy". It takes a well balanced team, but the more outstanding parts a team has it would seem the better their chance of winning the WS.
I agree that a big payout to Kimbrel would jeopardize our chances of keeping other players. We might be better off with, say Joe Kelly, as our closer but if the team is going in that direction they need to improve significantly in other areas to avoid needing a lights-out closer.