The Mets selected Thornton's contract from Triple-A Syracuse ahead of his scheduled start Wednesday in Washington.
New York optioned reliever Daniel Duarte to the minors to clear room on the active roster for Thornton, who will be making his MLB debut Wednesday. The 24-year-old lefty will get a look in the New York rotation after he compiled a 3.55 ERA, 1.18 WHIP and 33:10 K:BB over 33 innings across six starts between Syracuse and Double-A Binghamton. Though Kodai Senga (spine) seems to be trending toward a return from the injured list in the next couple weeks, the back end of the rotation has been a trouble spot for the Mets all season. With that in mind, Thornton could end up sticking around in a starting role on a more permanent basis if he's able to find success in his initial opportunities with the big club.