Oakland (54-37) is 11-0 all-time versus Pittsburgh, the best record in the major leagues by one team against another in interleague play. The A's recorded their 10th victory in 13 games Tuesday by defeating the slumping Pirates 2-1.
Brandon Moss drove in both runs for Oakland on a fourth-inning homer while his former team was held to three hits. Pittsburgh suffered its season high-tying fourth consecutive defeat and season-high third in a row at home.
The Pirates (53-36) have scored six runs during their four-game skid after totaling 16 in the previous three, wasting a strong effort by a pitching staff that's compiled a 2.58 ERA in the past five.
Runs may again be hard to come by for Pittsburgh on Wednesday. Oakland has allowed two in both games of this series and has a 2.03 ERA in the last seven contests.
"I just love the fact that this is part of the road you're on during the season," Pirates manager Clint Hurdle said. "It's got every opportunity to challenge you but at the same time it's a chance to make you better tomorrow."
Liriano (8-3, 2.20 ERA) will try to end the Pirates' woes by adding to his win streak. The left-hander is 3-0 in his last three outings with a 1.66 ERA and recorded his first complete game of 2013 on Friday.
Liriano gave up two runs and four hits in a 6-2 victory over the Chicago Cubs, striking out seven.
"This was an exclamation point on what he has been doing," Hurdle told the team's website. "He knows the role he plays here now. Basically, the last two, three weeks he's been our No. 1, and he's acted like it."
Liriano gave up six runs in 3 1-3 innings of a 9-7 loss in his latest start against Oakland on Aug. 11 while with the White Sox. He's had mixed results versus the A's, giving up five or more earned runs four times in 12 career starts but allowing one or none in five.
In his first start against Pittsburgh, Tommy Milone (8-7, 4.11) will try to take advantage of a struggling lineup to record his third straight win. The left-hander has posted a 5.92 ERA in his past four starts, but he went 8 1-3 innings and gave up three runs in a 6-3 victory over Kansas City on Friday.
"I don't know if we've seen him better, especially on the road," manager Bob Melvin said. "He was just making his pitches and mixing it up."
Milone is 5-0 in 12 career starts against NL opponents despite posting a 5.00 ERA.