Bob Cook

Chicago Cubs general manager Jim Hendry said at a pregame press conference Tuesday that his acquisition of Cy Young-caliber pitcher Rich Harden from Oakland was not a response to division rival Milwaukee’s deal the previous day for reigning AL Cy Young winner CC Sabathia from Cleveland. “We’ve been working on Mr. Harden for a few weeks now,” he said.

But the Sabathia deal certainly hurried the timeline to acquire Harden and reliever/spot starter Chad Gaudin, who are going to be critical to the Cubs’ essential need the rest of the regular season — keeping the best record in the National League.

That’s because entering Tuesday night’s home game against Cincinnati, the Cubs had the best home winning percentage in baseball, .767, while middling along with a .435 road winning percentage. That’s the biggest disparity between home and away play in the majors, and that road record is the worst among the three teams (St. Louis being the third) fighting for two playoffs spots likely to come from the NL Central.

If the right-handed Harden, 5-1 with a 2.34 ERA in Oakland, stays healthy — a huge if, given his six trips to the disabled list in six seasons, including a stay at the start of this season because of a right shoulder strain — that guarantees the Cubs the best starting rotation in the NL. And it probably guarantees the Cubs will get the home-field advantage they desperately need in the postseason if Chicago is going to break its 100-year World Series championship-free string.

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It’s not so much that pitching is a problem for the Cubs on the road.

It’s that the Cubs’ No. 1 NL hitting attack gets cold away from Wrigley Field, making stellar pitching a necessity away from home.

Cubs’ opponents have hit .253 on the road, only 12 points higher than their .241 average at Wrigley. The on-base percentage disparity is .331 on the road to .308 at home, and the slugging percentage difference is .418 on the road to .386 at home. So in general, Chicago pitchers haven’t cratered their teams’ chances on the road — not even All-Star Ryan Dempster, he of the 10-0 record at home and 0-3 record on the road. Take out his one shelling against the Chicago White Sox, and Dempster’s ERA is better on the road (2.58) than at home (2.71).

The problem is Chicago’s hitters are batting .311 at home, and only .257 on the road. The on-base disparity is .391 to .331, and the slugging slips from .500 to .395.

The difference Harden can make is not that he’s a spectacular road pitcher; he’s 3-0 with 1.79 ERA at home and 2-1, 3.38, away. It’s that by having another strong arm to keep up with the one-two punch of Sabathia and Ben Sheets in Milwaukee, Chicago can earn itself a few extra wins wherever it’s playing.