The Pirates' game against the Tigers on Saturday was postponed due to weather and will be made up during a doubleheader Sunday, pushing Williams' regular-season debut back a day, Rob Biertempfel of The Athletic reports.
Williams will make his first start of the 2018 season during Game 1 of Sunday's doubleheader, while Chad Kuhl takes the mound for Game 2. During 31 appearances -- 25 starts -- for the Pirates last season, Williams logged a 4.07 ERA and 1.31 WHIP over 150.1 innings.