The trade deadline this season was remarkable. Aside from the sheer number of players that were traded, a lot of the excitement stemmed from the fact that nearly all the deals took place within the final week of July.
Of the four remaining LCS teams, three of the them were involved in major blockbuster deals. The Royals acquired Ben Zobrist and Johnny Cueto; the Blue Jays added David Price and Troy Tulowitzki; and the Mets traded for Yoenis Cespedes. All of these moves clearly had a significant affect on the playoffs, but perhaps none had a bigger impact than a deal that took place in 2012.
On December 16th, 2012, The Mets and Blue Jays agreed to a deal that sent R.A. Dickey to Toronto (along with Josh Thole and Mike Nickeas) in return for Wuilmer Becerra, John Buck, Travis d'Arnaud, and Noah Syndergaard. They couldn't have known it at the time, but that trade has had dramatic implications on the 2015 playoffs.
The alternate reality that never happened
If on December 16th, Alex Anthopoulos had decided that trading d'Arnaud and Syndergaard to the Mets for an aging knuckleballer who was coming off his best season was too much, the playoffs would have been drastically altered. Not only would Syndergaard be pitching for Toronto instead of New York, but d'Arnaud would likely be their starting catcher, rather than Russell Martin.
d'Arnaud played in 108 games for the Mets in 2014, and had a similar timeline for his ascension taken place in Toronto, the Blue Jays probably wouldn't have offered Martin a five year contract worth $82 million. Instead he might have found himself on the Chicago Cubs (who were considered a favorite to land the catcher), which would have kept Miguel Montero on the Diamondbacks.
Keeping Syndergaard and d'Arnaud would likely have meant that the Blue Jays wouldn't have needed David Price, and could have settled for a complimentary piece like Mike Leake or Scott Kazmir. The Dodgers and Giants were known to have interest in the left-hander, but after missing out on Price and Cole Hamels, both teams had to settle for other options.
Perhaps the biggest "what if" from all of this however, is the question of whether or not the Mets would have been able to make the playoffs. New York finished seven games ahead of the Nationals in the NL East, and the Mets won 13 of Syndergaard's 24 starts. While they still could have won those games with another pitcher, it's safe to assume that things would have gone differently, and that the race for first place would have at the very least been much closer.
It's impossible to know exactly what would have transpired if Anthopoulos hadn't traded for Dickey almost three years ago, but it's clear that it would have had far reaching implications. Not only would the Blue Jays and Mets look vastly different, but so too would the entire playoff landscape.