Gibson had been worth 1.6 fWAR / 1.8 bWAR in the first half. If he duplicates that in the second half, and then repeats it in 2019 with -0.5 WAR for aging, he could produce ~4.4 WAR. At $8 mil per win, that would be worth $34.4 mil. His remaining salary is $2.1 million this year, plus arbitration next year which could be $8 mil coming off a good season. So his net value could be $34.4 minus $10.1 or roughly $24.3 mil. Looking at the Yankees, Justus Sheffield is a 55 FV pitching prospect at Fangraphs, which they valued at $22 mil last year, so it's not far off. Of course, assuming that Gibson has it all figured out is a pretty big assumption. There is a lot more risk with Gibson crashing than, say, J.A. Happ, who has been a consistent 3.5-4.5 bWAR performer for the last 3.5 years. (Plus he's left-handed, if they prefer that.) If Gibson is for real, though, he does have the extra year of control. But if the Yankees could deal a lesser prospect like Adams or Tate for Happ, they could potentially deploy Sheffield in the 2019 rotation themselves and save $8 mil towards the luxury tax next year too. Probably what I'd be looking to do. And nothing is too urgent for them -- they largely have a playoff spot locked up, and the bulk of the wild card sorting will occur after the deadline.