Williams, however, can't lay claim to coming off a better start than San Diego right-hander Jordan Lyles (1-1, 2.53 ERA).
Lyles pitched seven perfect innings, 7 1/3 in all, giving up one hit and tying his career high with 10 strikeouts on Tuesday in a 4-0 victory over the Colorado Rockies.
"The fastball command was really good," Lyles said of his first win with the Padres.
He was elevated from the bullpen to the rotation just the week before that and will be making just his third start Sunday. Lyles didn't allow a run in 10 of his 13 appearances in relief.
Lyles' quality start was one of just 15 for San Diego but also one of six in the past 11 games -- including one by winning pitcher Clayton Richard on Saturday.
"It's huge," Padres manager Andy Green said. "It takes the stress off your leverage bullpen arms and everybody else. ... If you can get three guys out there that you're expecting quality starts from consistently, it take the stress off your bullpen, and lets your younger guys find their footing along the way."
Williams (5-2, 2.72), who has faced every National League team except San Diego, didn't match Lyles' last start in his outing Tuesday, a 7-0 win over the Chicago White Sox, but his fastball was humming and he pitched seven scoreless innings while allowing six hits and getting six strikeouts.
That followed a game the Pirates came back to win the previous week against the White Sox in Chicago after Williams gave up two two-run homers.
"It was a really strong effort, I thought -- a really good back-on-track outing for him," Pirates manager Clint Hurdle said of Williams' second time around against the White Sox.
Williams not only has been perhaps the Pirates' most consistent starter this season -- his five wins leads the team, six of his nine outings have been quality starts, and he has allowed more than three runs just once -- but he also has been stellar at home. He has allowed two or fewer runs in each of his four starts at PNC Park this season and in 13 of his past 14 there dating to June 27.
He'll get another chance at home Sunday when the Pirates (26-19) try to secure a series split against the Padres (19-28).
San Diego has taken two of the first three games, including a 6-2 win Saturday, and has won five of seven. The Padres have not won a series in Pittsburgh since they took two of three on Aug. 8-10, 2014.
Pittsburgh, which had won three of four and eight of 10, will go for a split after going 10-3-1 in their first 14 series, including 5-1-1 at PNC Park.
The Pirates are expected to activate second baseman and leadoff hitter Josh Bell from the disabled list Sunday. He has been out 30 games with a broken left hand.
The Pirates returned utility man Max Moroff to Triple-A Indianapolis on Saturday in order to recall rookie Nick Kingham, who made his third major league start and took the loss.
For San Diego, infielder Chase Headley cleared waivers and was released.