The basis of sabermetric analysis is the ability to isolate one player's performance and drown out the noise. FIP removes defense from pitcher analysis, wRC+ eliminates park factors and adjusts for the league, and WAR works very similarly, depending on which formula you subscribe to. But when it comes to roster construction, the surrounding team and park are active participants. This thinking is exactly why the Yankees focus on left-handed batters with power and left-handed pitchers with fly ball tendencies. The Yankees focus on players that fit their ball park, and also those who fit their existing team. Such is the same with this offseason.
There are quite a few holes in the Yankees roster. There's the obvious black hole at shortstop, and there is the obvious concern of replacing (or reproducing) the production of Hiroki Kuroda and Brandon McCarthy. I think that both of these moves--for shortstop and starting pitcher--are wholly related.
Brandon McCarthy and Hiroki Kuroda are ground ball pitchers, as we know. And the infield defense in 2014, as we know, was pretty horrible for much of the season. So it would be logical that if the Yankees are going to sign ground ball pitchers, then they should sign a good defensive shortstop; and if they choose to sign a fly ball pitcher, then they can focus on an offensive shortstop.
The following are defensive ratings (through UZR/150) for the four shortstops on the free agent market:
Well, it's pretty obvious what a proper matching would look like. If the Yankees sign Hardy--who is already the most attractive shortstop on the market--then Brandon McCarthy would be the perfect pairing. This year he had a career-high 52.6% GB% and still did incredibly well despite a poor defensive infield. With someone like Hardy (or even Lowrie, if they want to save money), the number of runs saved would only be amplified. The same can be said about Hiroki Kuroda (48.6% career GB%), but there's a slim chance that he returns.
If you take a look at Brandon McCarthy's spray chart, this would echo that sentiment:
That's a whole lot of batted balls in the infield area. To be fair, a lot of those batted balls can also be found in other areas around the horn, but shortstop is an area that they can choose who to put there, more or less. I can absolutely imagine some of the hits to the left side being converted to outs with a stellar defensive shortstop.
Someone like Max Scherzer, on the other hand, tells a vastly different story with his batted balls:
Clearly, there are fewer ground balls overall by a significant margin. If the Yankees wanted to pursue someone on the left side with more offensive upside like Hanley Ramirez (even with the warts, that would be understandable given their offensive woes), they could more so put up with defensive incompetency knowing that they would make poor plays at a lesser rate. I don't think they would go after both Scherzer and Ramirez, but you get the idea in regards to any fly ball pitcher. The same would apply to both Cabrera and, to a lesser extent, Lowrie.
It's pretty unclear as to who the Yankees will pursue this offseason given the obvious financial constraints. The organization is committed to nearly $170 million without even taking into account arbitration eligible players and bonuses, so they may only have $20-30 million to play with anyway. But whoever they do decide on acquiring, they need to make sure that they complement each other in a way that is logical; this will assure that they will minimize their faults, and maximize their strengths.