Lohse is 9-2 in his career against the Pirates, who will try for their ninth straight victory Sunday and a three-game home sweep of the Milwaukee Brewers.
Pittsburgh (50-30) owns baseball's best record thanks to its longest win streak since a 10-game run June 26-July 5, 2004. The club has won 50 games before the start of July for the first time - the closest it had come to accomplishing that feat was the 1971 team that won its 50th game July 1 and captured the World Series.
"We're playing good baseball," manager Clint Hurdle said. "It's nice to get to 50 wins but we're just trying to meet the demands of the game, honestly self-evaluate and get better every day. There is still a long way to go."
Pedro Alvarez is enjoying a career-high 12-game hitting streak in which he is batting .396 with six homers and 15 RBIs. He hit his 20th homer in Saturday's 2-1 victory.
Alvarez has one hit in his last 14 at-bats against Lohse (3-6, 3.69 ERA), who is 4-0 with a 3.03 ERA in his past six outings against the Pirates. He's 5-1 with a 3.58 ERA in 10 career games at PNC Park.
Milwaukee (32-47) has won four of the right-hander's last five starts as Lohse has gone 2-0 with a 2.45 ERA. He beat the Cubs on Tuesday, yielding three runs over seven innings in a 9-3 victory.
While the Pirates have struggled to beat Lohse, Pittsburgh starter Charlie Morton (1-1, 2.81) is winless against Milwaukee.
Morton is 0-4 with a 6.67 ERA in six starts versus the Brewers, although he hasn't faced them since 2011.
The right-hander has failed to get through six innings in his first three 2013 starts, lasting 5 2-3 and giving up six runs last Sunday in a 10-9, 10-inning victory over the Angels.
The Pirates have enjoyed five straight home sellouts - the longest such streak since PNC Park opened in 2001.
"The energy of the crowds has been unbelievable and we've been soaking it all up," said closer Jason Grilli, who improved to 15-for-15 in save chances at home Saturday. "You absorb it and try to use it to your advantage. We're playing for ourselves but we're also playing for about 40,000 people in the stands and an entire city."
The Pirates also lead the majors with a 20-11 record in day games while the Brewers are 9-20 for the NL's worst mark.
Milwaukee has totaled 10 runs while dropping four straight and has gone 3 for 16 with runners in scoring position in this series.
"We've got to get big hits," manager Ron Roenicke said.
Carlos Gomez is 4 for 9 in this series and batting .378 with four homers and eight RBIs in the season series.
Pittsburgh has taken eight of 12 meetings and can complete its first three-game sweep of Milwaukee since Aug. 28-30, 2009.