Trade season is in full swing, and with it comes the uncertainty of performance in a new environment. Unless you’re Jose Quintana, being traded means a player has to deal with a new city, acclimatize to new fans, teammates, and possibly an entirely new league. With all that, it’s no surprise you often hear about players needing a “change of scenery” in the middle of a season.
After the Yankees acquired David Robertson, Tommy Kahnle and Todd Frazier last week, I was stuck trying to figure out the best way to project their performance for the rest of 2017. Moving from the AL Central to the AL East can wreak havoc on any pitcher, and the collection of bandboxes in the Yankees’ division could help right Todd Frazier’s season to a certain extent. All of this lead to a recurring question: how do traded players perform with their new teams? Can historical trends provide any clues?
I began by aggregating all the trades made for MLB regulars over the last five Julys. This means no prospects, since it’s too difficult to juggle different farm systems, discrepancies in different levels or leagues. The Pacific Coast League is far better for hitters than the International League, so a move could unfairly boost or penalize performance. I also filtered out every player who was injured, since injury risk is pretty uniform for all players. This left me with 119 players, whose pre-trade performances are displayed below:
I used fWAR/650 PAs for position players, in an attempt to extrapolate their half-season performance into a full season. fWAR/100IP for pitchers was used to roughly equate reliever and starter value. The post-trade plots? See for yourself:
If these plots all look similar, don’t worry. Overall, it appears players perform at roughly the same level pre-and post-trade. Hitters log a 92.77 wRC+ and 1.46 fWAR/650 before being dealt, and a 90.60 wRC+ with 1.43 fWAR/650 after. For pitchers, the difference is slightly more noticeable, 3.81 FIP and 1.24 fWAR/100 pre-trade and 3.76 FIP with 1.07 fWAR/100 post-trade, although none of these are significant differences.
Trade deadline players generally fall into one of two buckets: overperforming and underperforming. Tommy Kahnle would be an overperformer, given that this is the best season of his career, by a wide margin. Likewise, Todd Frazier would be considered an underperformer, playing below his career line this year. Neither of these examples mean that this season isn’t a new normal, but typically players will regress to their career norms over the course of an entire season.
This regression works both ways, and is one of the reasons why performance stabilizes pre-and-post trades. Overperformers come back to Earth and underperformers recover some value. A good example of this is Abraham Almonte, a perfectly fine, average major leaguer. Almonte’s been traded twice in the last five Julys while struggling (average 53 wRC+) and then rebounds in his second half with new teams (102 wRC+ average post-trade). Frazier, in an extraordinarily small sample size, has recovered some value already, with a 109 wRC+ since being traded.
There is a third bucket of traded players, and it’s the Mr. Consistencies. Some players don’t register much of a change in performance at all. Andrew Miller, Ben Revere and others have stayed consistent despite being dealt, which makes projecting their performance a little easier.
If I were to give my best guess for the future performance of our three new Yankees, I’d say we have one in each of the three buckets. Kahnle will probably regress slightly, although I think his stuff is legitimate enough that he won’t lose much absolute value. Frazier will probably regress positively, giving the Yankees a deeper lineup and more production from the corner infield. Robertson, meanwhile, has been incredibly consistent in his performance and peripherals over the past few seasons, and that shouldn’t change too much.