The Cardinals got an early rally against the unlikeliest of pitchers, but it was an early move to a most reliable pitcher that spun those runs into a win. With the Cardinals clinging to a three-run lead Saturday and the tying run at the plate in the sixth inning, manager Mike Matheny called for Carlos Martinez, the righty who exited spring designated as the club’s setup man. Instead of being bound by convention — the setup man pitches the eighth, holding a lead for the closer — Matheny went with prevention. The top of Pittsburgh’s order was up and a game the Cardinals won 6-1 was in doubt. This was Martinez’s situation, even if it wasn’t his inning. “It’s just seemed like a spot we had to get out of,” Matheny said. “We got into a jam. I like Carlos coming in at that point to get us out. I don’t know how it’s going to play out from here. I don’t think that’s going to be completely out of the question, though. We’re trying to find the best way for him to make the biggest impact.” Martinez stranded the two runners he inherited and pitched a scoreless seventh before the Cardinals added on late against Pittsburgh. Home runs by Yadier Molina and Jhonny Peralta added to the 3-0 lead the Cardinals took in the first inning on Pirates lefty Francisco Liriano. Starter Joe Kelly traipsed around trouble but kept the lead through his 5 1/3 innings of work, and the only run the righty allowed came on a bases-loaded walk. It was the two groundouts that Martinez promptly got to end the sixth that led to the win. It also signaled the way Matheny might seek relief. Smarting from a 12-2 loss Friday night in their first game of the season at PNC Park, the Cardinals brought into Saturday’s contest a bullpen built so far on quicksand. The lingering question of spring training was the final spot in the bullpen, and not one of the four relievers auditioning for the spot seized it. In the small sample size of four games, the Cardinals’ bullpen had the biggest ERA in baseball (9.58), but that was bloated by its seven runs allowed Friday. The late-inning constants for the Cardinals, however, had been closer Trevor Rosenthal and the left-right combo of Kevin Siegrist and Martinez.