The majority of the writing and conjecture involving the Yankees of late has revolved around the notion that this season is all but over. The team is once again a game below .500, and their run differential yields a Pythagorean record of 33-38 (a 75 win pace). And while they have not be awful, the sense of pessimism is nothing short of pervasive. As a result of this, there have been plenty of discussions regarding who should be dealt, and who should be kept to be a part of the next great Yankees team.
As of now, there is no strong consensus in this matter, outside of the free agents to be and the players that we wish we could ... well ... wish away. Didi Gregorius is one of the most polarizing players in this respect, and he is young enough to be a part of the future core, yet unexciting enough that some feel he isn't worth keeping around (though, the presence of Jorge Mateo may be the cause of that) - particularly if he can fetch something of value. So where does the truth lie?
Gregorius is a middle-of-the-pack shortstop thus far in 2016, placing 14th among 26 qualified players in wRC+, and 18th in fWAR. He was better last year, placing 4th among 20 in fWAR and 9th in wRC+ - the big difference here lays in his defense, which was (based on the metrics, at least) well above-average in 2015, and well below-average this year. If the truth lays somewhere in the middle, Gregorius is a rather average shortstop.
There are hints of more upside, though, both at the plate and in the field.
In 2015, Gregorius was horrific in April, batting .206/.261/.238 (36 wRC+) in 69 PA, leading to immediate calls for his head. Over the next five months (509 PA), he hit .273/.326/.387 (96 wRC+), improving slowly in May and June before breaking out over the Summer. Gregorius appears to be following that pattern again in 2016 - he hit .224/.254/.343 (56 wRC+) in April, and has hit .311/.347/.449 (115 wRC+) since. If he can get to the root of his slow start issues, it's entirely possible that he can be a tick above-average as a hitter (and comfortably above-average for the position). He's actually batting .287/.333/.408 (101 wRC+) over the last calendar year - a stretch of 596 PA - so the potential for consistency is there.
Defense is much harder to analyze, but there are reasons to be optimistic, as well. Gregorius' glove has been regarded as above-average or better for quite some time - check out here, here, and here for some examples of praise from his prospect days. His defensive metrics have been all over the place in his short Major League career, but, taken as a whole, tell the story of an average shortstop. He has made more errors this season, and has made some noticeable mental errors - but I would argue that he is a reliable defender overall.
So what does it all mean? If Gregorius is an average hitter (which he has been over the last calendar year) and an above-average defender (which he has the tools to be, and was last year), he may well be an incredibly valuable player. That alone makes it worth holding on to him barring some sort of no-brainer deal popping up. The flashes that Gregorius has shown in his time in pinstripes are encouraging, and he's still just 26.
Moreover, it isn't as though the aforementioned Mateo is forcing the issue, either - he's still at High-A, where he's hitting .203/.230/.220 in June (and .267/.311/.398 against RHP overall). And having a good shortstop in the Majors with another one knocking on the door in the minors is a good problem to have.