PITTSBURGH (AP) — Falling out of first place and an anemic offense are hardly the biggest problems for the St. Louis Cardinals at the moment. Now, they've got to find a way to stay in a playoff race without franchise cornerstone Yadier Molina. The All-Star catcher left with a sprained right knee after the third inning of a 6-0 loss to Pittsburgh in the second game of a doubleheader on Tuesday night. Molina will fly to St. Louis on Wednesday for further examination and expects to be placed on the disabled list. Molina has been dealing with inflammation in the knee for more than a month. The pain simply became too unbearable to go on. "I tried to play through it but it's getting worse," Molina said. "The smart thing is to take time off and try to fix it." Molina allowed the Pirates to take an early lead in the second game with a rare passed ball and was in obvious discomfort during his two at-bats. The Cardinals replaced him with Rob Johnson in the top of the fourth and aren't certain when Molina will be able to return. The timing couldn't be worse for a slumping offense that now must replace the second-leading hitter in the National League. St. Louis has scored just five runs during its season-high, six-game losing streak and put together nine hits in 20 innings on Tuesday. "That's the sad part," Molina said. "I want to be here for my team and for my teammates, but the smart thing to do is take care of my knee and come back as soon as possible." The injury came hours after general manager John Mozeliak insisted the Cardinals aren't panicking even as the Pirates leapfrogged them in the NL Central standings. "I still think it's a good team," Mozeliak said. "There's definitely ups and downs and peaks and valleys in every season and this is certainly a down time for us." And an up one for the Pirates. Alex Presley hit a sharp grounder that deflected off the glove of St. Louis reliever Kevin Siegrist (0-1) and away from shortstop Pete Kozma in 11th inning of the first game, giving Pittsburgh a 2-1 victory. Kozma could not recover and the ball rolled into the outfield, allowing Russell Martin to sprint all the way home from second base. The bounces didn't get any kinder a few hours later. While Pittsburgh rookie Brandon Cumpton (1-1) kept the NL's top offense in check, Pittsburgh poured it on with a little help from St. Louis left fielder Matt Holliday. The Pirates took a 2-0 lead on Jordy Mercer's RBI single in the fifth before McCutchen stepped in. He drilled starter Tyler Lyons' pitch deep to left but Holliday appeared ready to track it down at the wall. Instead, the ball popped off the heel of Holliday's glove and into the stands. Lyons (2-4) placed both hands on his head in shock while the packed bleachers let Holliday have it. Holliday's night didn't get any better an inning later when he overran Josh Harrison's flyball to the wall, allowing Harrison to make it all the way to third. "It's a hard game," St. Louis manager Mike Matheny said. "Our guys have been making a lot of good plays. Every once in a while there's tough ones you don't make." Pittsburgh has outscored St. Louis 17-3 through the first three games of the pivotal five-game series. "It's an opportunity for us to find out what we're made of," Matheny said. "These are the times that define you. They happen during the season -- never fun when you go through them, but we'll see what kind of fight you have." The Cardinals can rely on one of the best pitching staffs in the majors, a status Lance Lynn did little to jeopardize while dueling with Pittsburgh's A.J. Burnett in the opener. Pitching without the usual run support he receives, Lynn matched Burnett strike for strike in six taut innings. Lynn allowed a run on three hits, walking two and striking out seven. Still, it wasn't enough to halt a slide that's in danger of turning into an extended slump. "It's just one of those points in the season -- you have your ups and downs, and hopefully it's the only down we have and we can move on tomorrow and get a win tomorrow and get back going in the right direction," Lynn said. NOTES: The series continues on Thursday. Adam Wainright (13-6, 2.51 ERA) starts for the Cardinals against Jeff Locke (9-3, 2.15) ... St. Louis sent struggling reliever Marc Rzepczynski to Cleveland on Tuesday in exchange for minor league infielder Juan Herrera. Rzepczynski had a 7.84 ERA in 10 1-3 innings this season with the Cardinals ... Pirates 2009 first-round pick Tony Sanchez went 0 for 3 with an RBI in his first major league start at catcher.