The Mets already have had two minor league players that have elected for free agency: Jack Egbert and Garrett Olson.
Both players were far, far down on the depth chart coming out of Spring this past year, and they each pitched in a singular MLB this season:
Egbert (May 28), 0.2 IP, 0 H, 0 R, 0 K, 0 BB
Olson (Aug 8), 0.1 IP, 3 H, 4 ER
I was at that game that Olson pitched (the Mets lost 13-0). Since that was the only game that Olson ever pitched in a Mets uniform, his career ERA as a Met is 108.00.
As you can tell by the numbers (in terms of usage), this is not a loss to the Mets organization.