Williams will start Wednesday's series finale against the Tigers, Adam Berry of MLB.com reports.
Williams originally lined up to start Friday against the Giants, but with two off days this week and Chris Archer now serving his five-game suspension, the Pirates will opt to push Williams up one game. The 26-year-old has a 2.45 ERA, 0.98 WHIP and 12:4 K:BB over his first three starts (18.1 innings).