In 2014, the Yankees had one of the worst middle infields in baseball. Second base was a revolving door all season that included a broken down Brian Roberts and "enough said" Stephen Drew. Shortstop was held down by a legend in Derek Jeter, but even the most ardent Jeter fans realized he was a shell of his old self that year.
The Yankees' combined fWAR between second and short that year was -2.0, the worst in the majors. Both offensively and defensively, it was ugly. Fast forward to 2016, and the Yankees seem set to have one of the better middle infield duos in baseball as Starlin Castro will man second and Didi Gregorius will play shortstop. Both are young, exciting players with a ton of promise.
Offensively, they've had varying levels of success. Gregorius was a very light-hitting shortstop up until the second half of last season when he turned it around. Starlin Castro was once one of the top prospects in baseball in part due to his bat, and while he hasn't completely lived up to the hype, he is a three-time All-Star with three seasons of a .292 or better average and at least a 100 wRC+. In 2016, there's reason to be believe that both could be impact hitters.
Gregorius struggled early on in the Bronx last season; he had a first half slash of just .238/.293/.326, a measly 70 wRC+. He wasn't hitting for power, or at all, really. By the second half, Didi turned it around, looking like a completely new player. After the All-Star break, Gregorius' slash shot up to .294/.345/.417, and his wRC+ vastly improved to 109. He really improved across the board. He was striking out less, walking more, hitting for more power, and making better forms of contact (less ground balls, more line drives). FanGraphs had him ranked as the 8th best hitting shortstop in baseball last season, and he'll only get better. As he enters his prime at just 26 years old, Gregorius should take another step forward offensively and could push hitting .290.
Starlin Castro, meanwhile, might not have completely lived up to the hype, but he's certainly no slouch at the plate. Through the first five seasons of his career, 2013 was the only one where he was a clearly below-average hitter. All his other seasons, outside of 2015, were pretty good though.
In 2010 and 2011, he had at least a .300 average and .340 OBP for Chicago. In 2012, his slash dropped to .283/.323/.430, but he jacked 14 homers, drove in 78 runs, swiped 25 bags, and recorded the best fWAR of his career with a 3.1 mark. He had a down 2013, but he was back at it in 2014, slashing .292/.339/.438, with 14 home runs and a 2.8 fWAR in just 134 games.
Last season was an interesting one for Castro. He started off the season at shortstop, but made the move to second base to make room for Addison Russell. Logically, there's no reason your hitting should be impacted by what side of second base you line up on in the field, but for Castro, the results were staggering. In 107 games at shortstop, he had a 59 wRC+, but at second, he had an outstanding 154 wRC+. He'll be the full-time second baseman in the Bronx this season, and coupled with a change of scenery, there's a chance the soon-to-be 26-year-old makes good on all of his promise.
So offensively, they're two guys that have proven they can hit, and are in a good position to get even better, but they should be solid defensively as well. Gregorius is already one of the best defensive shortstops in the game. He has great range and a cannon for an arm. It was the main reason the Yankees were attracted to him a year ago, and he proved them right; he was the fifth-best shortstop in baseball last season per FanGraphs' defensive metrics.
As for Castro, we don't have much to go off when it comes to his defense at second, but there's reason to be optimistic. He was viewed as a good defender at short, backed up by a positive defensive rating by FanGraphs every season of his career outside of 2011 when he just missed with a -0.3 mark. He looked pretty solid at second last season, and shortstop is usually viewed as the harder position to play, so it's likely that Castro should be a solid defender at his new position.
Hopefully, it's clear by now that the Yankees' middle infield is going to be quite good, but it's even more impressive when you consider how they acquired the players. Gregorius was acquired last offseason for Shane Greene, while the Yankees landed Castro in December for Adam Warren and Brendan Ryan.
A after the Gregorius trade, and Brian Cashman is probably wanted by the authorities for highway robbery. Didi was the fourth best shortstop in baseball by fWAR, while Shane Greene had an ERA of 6.88 across 83.2 innings with Detroit. The Castro trade can't be judged yet, but Brendan Ryan has the power of a sports blogger and was already released by Chicago. Adam Warren was a valuable piece of the pitching staff last season, but when you can trade a backend starter/middle reliever for a 25-year-old, three-time All-Star middle infielder, you do that 11 times out of 10. Overall, with Ryan and Greene basically being non-factors, the Yankees essentially subtracted Warren and added Castro and Gregorius. Not bad.
Middle infielders who can hit are traditionally never in high supply. The Yankees have two guys that could have top ten offensive seasons at their respective positions, and both should be at least solid defenders with Gregorius leaning more towards spectacular. They're both just 26 and should be around for awhile. It's certainly not a bad upgrade from Roberts/Drew and a 40-year-old Jeter two years ago, and all it took was a light-hitting back up middle infielder, a basically Four-A starter, and a backend starter/middle reliever. We tip our hats to the Yankee front office.