The playoff odds are courtesy of CoolStandings. For the sake of ease I only plotted four points per month: the 1st, 8th, 15th, and 22nd, or a day offset if there were no games on those days (4/1 became 4/2 and 7/15 became 7/16). Baseball Prospectus also has playoff odds but I couldn't quite figure out how to get historical figures (i.e. not just the current odds). It didn't much matter as CoolStandings was proved more than adequate for this little exercise.
It's fitting that Jose Reyes is at bat in the background picture, since the season really fell apart when he got hurt. Not that I believe that the Mets would have prospered with Reyes given the rest of the injuries and ineptitude, but they really did miss him.
The Mets and Marlins were healthy opposites of one another until around midseason when the Marlins fell apart and the Mets, having already fallen apart, continued their speedy descent.
The Nationals practically flatlined right out of the gate.