Go figure.

One night, the Pirates get mowed down by a pitcher with an 8.31 ERA.

The next, they bench their top two RBI producers and beat up on the pitcher with the National League's best ERA, chasing Houston's Wandy Rodriguez on five runs over 4 2/3 innings to flatten the Astros, 7-4, tonight before a standing-room-only crowd of 37,167 at PNC Park.

Further, go figure that Jeff Karstens, unable to last longer than six innings in any of his first eight starts, turned in his finest showing of 2009 with seven innings, two runs and an efficient pitch count of 87, with 60 strikes.

Matt Capps, returning from that line drive that bruised his elbow Monday in Chicago, got the final out for his 10th save.

Eric Hinske had three singles and a walk, Jack Wilson two doubles.

Manager John Russell, visibly displeased after Houston's Brian Moehler bucked that 8.31 ERA for a complete game the previous night, gave a rare jolt to the lineup: Struggling Nate McLouth and Adam LaRoche were benched, steady Andy LaRoche was bumped up from his usual No. 6 spot to No. 2, and bench men Craig Monroe, Delwyn Young and Hinske were inserted.

"We're trying to utilize our offense right now because we're ??? I wouldn't say we're in a rut, but we're trying to give ourselves the best chance to win," Russell said.

He could not have imagined it would be so effective against Rodriguez, whose 1.71 ERA was second in Major League Baseball only to the Kansas City Royals' brilliant Zack Greinke.

As it was, the Pirates wasted no time in wearing down Rodriguez, scoring three times in the first. That included RBI singles by Freddy Sanchez and Monroe, as well as a sacrifice fly by Robinzon Diaz. The first five batters reached safely and, before Rodriguez settled, he had to run his pitch count to an early 32.

Houston nibbled away at Karstens for a run in each of the third and fourth innings, but the Pirates chased Rodriguez after 4 2/3 with a two-run fifth: After two outs, Eric Hinske walked to put runners at the corners, and Young and Diaz followed with RBI lasers to left for a 5-2 lead.

Rodriguez's ERA now: 2.26.

Back-to-back doubles by Wilson and pinch-hitter Brandon Moss in the eighth brought an insurance run and, after one out, another by Andy LaRoche made it 7-2.

Loudest roar of the night -- in addition to those let out when fans when learn of the Penguins scoring in Detroit -- went to center fielder Nyjer Morgan for a face-first diving catch of pinch-hitter Darin Erstad's liner in the seventh.