Williams is scheduled to start the second game of Tuesday's doubleheader with the Marlins, Field Level Media reports.
Taijuan Walker will get the "start" for the first game of the twin bill, which is the resumption of a game that was suspended with one out in the top of the first inning back on April 11. Since the nightcap will be a seven-inning game, Williams should have a good chance to factor into the decision even if the Mets decide to cap his pitch count, given that he's made a pair of relief appearances of only two innings and 2.1 innings since being called up from Triple-A Syracuse on Aug. 16. Williams will likely return to a bullpen role after the spot start.