Williams will start Saturday's game in Atlanta, Anthony Rieber of Newsday reports.
Williams' most recent appearance came in the second game of a doubleheader with the Marlins on Tuesday, when he followed opener Noah Syndergaard and covered four innings out of the bullpen. Though Syndergaard is on tap to serve as an opener again in Sunday's season finale, the Mets won't have Williams follow him, as the right-hander will instead get the chance to pick up his 16th start of the season a day earlier. Because he'll be returning to the mound on three days' rest, Williams likely won't be asked to cover more than 4-5 innings.