For those who haven't noticed--or for those who have been living under a rock for the past month--Didi Gregorius has been playing very well. He's been playing so well, in fact, that he is now up to 2.4 rWAR, 2.2 fWAR, and 1.7 WARP on the season. He is now also up to 92 wRC+, which would be tied for the best offensive season in his career. Hitting .327/.364/.433 after the All-Star break can have that effect.
There will certainly be a lot of excitement about Gregorius' recent hot streak, and rightfully so. This a very young player on a team with a dearth of young position players, and many fans and writers may have high hopes about him being part of some post-Derek Jeter core. I don't think I'll take my enthusiasm that far, but I do think this most recent stretch, as well as his full body of work, has proven a few things.
Firstly, this season proves that Gregorius can be an average offensive shortstop, and that's hugely important. We all knew this winter that he was defensively proficient, but there were serious questions about his bat. Even though he hit at a 92 wRC+ clip in his rookie season (which is above average for a shortstop), he followed that up with a very poor 2014. This could have been because of the Diamondbacks' coaching failures, or because he had a questionable role on the roster with Chris Owings breathing down his neck, but the concerns were still real. If he hit like he did in 2014 this season, there would certainly be hand-wringing. Funnily enough, Owings is hitting .239/.269/.340 this year, much worse than Gregorius' offensive floor.
Most importantly, though, this all proves that Gregorius has a place on this roster for at least next year. The options for free agent shortstops this offseason are incredibly flawed, to say the least. There's Asdrubal Cabrera, who has had a decent year with the Rays (102 wRC+ in 452 plate appearances), but his defense is really below average, and he'll likely be forced to second base in the near future.
There's Ian Desmond, who is an incredibly complicated player. He has had years that were offensively brilliant, like when he hit .292/.335/.511 with 25 home runs in 2012, and then this year, when he hit .234/.285/.395. There's no guarantee he'll even be an average shortstop, and he's turning 30. The rest of the lot would be one-year stop gaps: Jimmy Rollins would likely garner a decently expensive flyer contract, and Stephen Drew will likely get the same. So, there would be a lot of uncertainty in that market, and in the trade market, one can easily guarantee that Brian Cashman would have to give up more than Shane Greene this time around.
Didi Gregorius, depending on how you interpret defensive value, is having one of the best seasons for a Yankees shortstop since Derek Jeter's 2009 season. Jeter's last season, in fact, was so horrid by some standards that Baseball Prospectus' WARP considers him the worst player of the 2014 season. That would make Gregorius a four win upgrade, or the equivalent of Jose Altuve or Edwin Encarnacion, for example.
He is also going into his first year of arbitration, and glove-first shortstops don't get paid spectacularly, especially in the first two years. Brandon Crawford, who is a decent comparison, got $3.2 million for his first year of arbitration. So not only are the Yankees decently sure they have a league average shortstop, but he's likely $10 million (per year) cheaper than a similar free agent.
Now, baseball is very hard to predict. This could of course be smoke and mirrors, and this could also be recency bias. The progression of players is rarely predictable or linear, but based on the information we now have, Gregorius has had over 1000 plate appearances. He has put up offense that is average in comparison to his peers, and his excellent defensive work puts himself above them. I honestly don't see his bat getting that much better, but if this is the player the Yankees are getting for the next few years of team control, then it's a success. For this "new look" Yankees team, Didi Gregorius is likely at the center.