Three weeks to go before the deadline, NY still reportedly going hard after a SP, and possibly after yet another back end reliever too (if this happens, it makes me more nervous about Betances' return). Let me take a crack at handicapping the possibilities:
Matt Boyd (DET): Much more team control than the others and so he will cost more, also could be packaged with Shane Greene. I think the prospect price here will be not quite worth it for Cashman, I think Boyd goes to the Astros.
Trevor Bauer (CLE): I don't believe they will trade him but if they do, I have said since the offseason that I think it will be to the NL, maybe the Padres. The last thing CLE needs is to have Trevor Bauer beating them in playoff games.
Marcus Stroman (TOR): This seems like the most likely, he is probably a #3 but under contract through 2020 and would give NY another option to fit somewhere in their postseason group. I would hate to move Clint Frazier within the AL East but unless they can figure out a match from the very young side (Florial/Gil and Wade, maybe?), Clint probably has to be part of this. I would love if this happens to get Giles too (both Stroman and Giles are under contract through 2020).
Zach Greinke (ARI): ARI hasn't decided if they are selling or not yet and Robbie Ray was rumored to NY but to me Greinke is a better fit. He would not have been when he was younger but he is almost 36 now and the closest thing to an ace that might be available. I think NY could even move the last year and a half of Ellsbury's deal in this, Greinke is owed so so much more and Ellsbury has Arizona roots, he grew up in part there and runs a baseball camp every summer there and I believe he has a house there. Obviously NY would have to include Clint Frazier and more in addition to those two, but I could see this one happening too if ARI falls out of it more in the next week or two.
Madison Bumgarner (SF): It's hard to imagine NY's analytics matching up with SF's likely asking price here, plus somehow SF is currently only 5 1/2 games out of a wild card. This one was always pretty unlikely to me, just not sure he has the stuff anymore.
Anyone from the Mets: I will believe it when it actually happens and not before, I would not hold my breath. Besides the Wilpons' understandable inferiority complex, Brodie got ripped off badly by DiPoto, who Cashman seems to take advantage of a few times each year. Brodie I don't think has the balls to match his player evaluation with Cashman and co., but we'll see. Also Wheeler is like Burnett or Pineda, amazing stuff but completely unreliable, I don't see it.
Clint is pretty expendable now, his bat is legit (.843 in 191 PAs at 24 this year) but he is behind Judge/Stanton/Hicks and now even Gardner looks like he might stick around for yet another season. NY needs a second OF who can play CF adequately behind Hicks, Judge can occasionally but ideally not for a prolonged period, Stanton no, Tauchman can but hasn't hit much yet, and Gardner is up to 15 HRs already with again solid D, so maybe he is back again next year, leaving Clint as the 5th option in a 4 man OF again. DH could open up again if they don't pick up Encarnacion's option, but Andujar should be back in the picture there also.
So if none of the above work out to Cashman's satisfaction, I can still see him trying to flip Clint for the rough equivalent in a SP prospect, my suggestion earlier was Bryse WIlson from ATL. TB got Tyler Glasnow last deadline, Giolito maybe could have been gotten last summer when he was horrendous, maybe Cashman can find someone like that who no one is rumoring. There are only a handful of genuine playoff impact 'aces' and outside of maybe Greinke, I don't think any of them are moving this month, but adding SP depth is always good.