MLB trade winds blow in July and the offseason

Each season, MLB teams complete in the neighborhood of 10,000 transactions. Some are mundane, like Jesse Chavez changing his number to 22 this offseason, while others, like being designated for assignment, have a huge impact on a player and his family. Today I'll talk about one of the most exciting type of transactions for fans: MLB player trades.

Before I dive into the trade patterns of the past five years, I'll clarify a few things. For the purpose of this analysis, I’ve defined each season as beginning in October of the previous year. That means that the 2014 trading season began on October 1, 2013 and ran through to the end of September 2014. I’ve done this so that each player traded has the chance to impact the MLB season of the team to which he is traded that season, even if he may not qualify for a playoff roster.

Over the past five seasons, the pattern of trades has remained remarkably consistent, despite changes in both the structure of the playoffs and the way free agent draft pick compensation is distributed. Each year, 40-45% of trades will occur during the offseason. Of these, most occur in December and early January. Ever wonder what it’s like to wake up on New Year’s Day (perhaps you’ve been over served) to find out you have to move to another country for work? You could always ask Jason Frasor, who was traded from the White Sox to the Blue Jays on January 1, 2012.

Not surprisingly, the non-waiver trade deadline makes July the busiest month for trades each season. In the past five seasons, there have never been fewer than 27 trades in July, and most come in the latter half of the month. Players can be traded after this deadline, but the waiver process makes things more complicated. August is the next busiest month as GMs make a push to add players that are eligible for their playoff roster.

Despite an increase in the number of trades over the past few years, the total number of players changing teams has fluctuated as has the percentage of trades including players who saw time in the major leagues that season. These players may have played for the team they were traded from, traded to, or both; however, fWAR represents the wins above replacement accrued by MLB players traded during that entire season, not just for the team that they’re traded to. Some players are traded more than once. Johns Buck and McDonald are examples of players who were traded three times in a single trading season. In these cases, I’ve counted their fWAR each time they were dealt.

While most of the players traded each season are not household names, there are usually a couple of blockbuster deals each year. This offseason, we’ve already seen A.J. Preller trade for what could be a dozen wins. In 2010, Cliff Lee (7.0 fWAR) was acquired by Jack Zduriencik in December only to be flipped to Jon Daniels' Rangers that July. That same season, Ruben Amaro Jr. traded for the Roys Halladay (6.1 fWAR) and Oswalt (4.3 fWAR). In fact, every season, at least one player traded has accumulated at least 5 fWAR. However, the percentage of fWAR of all traded players belonging to pitchers fluctuated from a high of 73% in 2010 (again, Cliff Lee x2 and the Roys) to 39% in 2011.

What about in-season trades? With pitchers snapping their UCLs left and right, does attrition rule the mound and force contending GMs to focus on acquiring pitchers? Typically, the 25-man roster is made up of 48% pitchers (5 SP + 7 RP), which lines up closely to the percentage of all players traded who pitch. It’s not conclusive that GMs whose teams are contending are dealing for pitchers; pitchers are traded at close to their proportional representation on an MLB roster both during the year as a whole and the season.

Now, it’s your turn. Is there anything you’ve always wanted to know about MLB trades but were too afraid to ask? I’ve built a crude database of trade details that I’ve pulled from MLB Trade Rumors and MLB.com, so don’t be shy and ask them here!

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All statistics courtesy of FanGraphs, MLB Trade Rumors and MLB.com .

Matt Jackson is a contributor to Beyond the Box Score. You can also read his work at Banished to the Pen. Follow him on Twitter at @jacksontaigu.