Chicago ? Turning up the heat.

It’s usually not what you want to do in the middle of a Midwest summer. But that’s exactly what the Cardinals have done.

By trading the occasionally electrifying Colby Rasmus in a short-sighted move that brought them Edwin Jackson, they have turned up the volume on an already pressurized situation. And they may have quietly telegraphed the end of the Tony La Russa era in St. Louis.

La Russa’s close friendship with White Sox Chairman Jerry Reinsdorf long has suggested they will work together again in the future. The Sox’s curious handling of the Jackson trade suggests this reunion could begin in 2012, assuming Ozzie Guillen gets money-whipped to jump to the Marlins after this season.

Rasmus is exactly the kind of young, (potentially) rising star the Sox have not been able to develop for themselves during the Ken Williams era. He was only made available, or so La Russa hinted on the eve of the trade, because he turned to his father/high school coach rather than sticking to the Cardinals’ program.

(Tony Rasmus vehemently denied the charge, saying La Russa had only his son to deal for much-needed pitching.)

But why didn’t the Cardinals just do a trade with the White Sox? Why not use Rasmus to get Jackson? Why turn this into a three-team combination of trades that left Rasmus in Toronto?

The White Sox would have cleared salary by doing Jackson for Rasmus more or less straight up, as the 24-year-old center fielder is earning only $443,000 this season. Sure, other players were involved, notably reliever Jason Frasor, but Rasmus is the big fish here, and the White Sox allowed somebody else to catch him, almost like they were guides rather than fishermen.

The Cardinals also got pitching depth to go along with Jackson (relievers Mark Rzepcyznski and Octavio Dotel from the Blue Jays), but the Sox continue to shop Matt Thornton so they could have put some pitching next to Jackson without waving a white flag for 2011.

It doesn’t look like the Sox really wanted Rasmus, and there are only a few answers for that: They believe he’s overrated, a tease who promises more than he can deliver. They think improving the bullpen is more important than adding to a lineup that ranks 11th in the American League in scoring. They are keeping the coast clear for La Russa to arrive next winter, after his work is done in St. Louis.

La Russa almost walked away from the Cardinals after the last two seasons, hoping for one more trip to the World Series behind Albert Pujols.

Both La Russa and Pujols will be free agents after the season, along with Jackson. The Cardinals have mortgaged at least some of their future with three years of moves La Russa’s will influenced as much as general manager John Mozeliak’s judgment. If they don’t re-sign Pujols, everything could change.

“This is a window to win,” Mozeliak said when he announced the trade. “Today we feel like we’re a better team than we were yesterday.”

But are they good enough to outlast the Brewers, who gave up four runs in three games to sweep the Cubs?

The National League Central leadership has been a changing proposition throughout July, with the lead bouncing back and forth between the Cardinals, Brewers and Pirates. The Brewers probably are the favorite even after the Jackson trade.

It’s probably easier to forecast what happens after this season than during it.

The Marlins want Guillen, and Guillen wants to be one of baseball’s most highly paid managers (why wouldn’t he?). La Russa wants to keep working in baseball and isn’t looking to start over with a new ownership group. There is no Guillen heir apparent in place, as bench coach Joey Cora probably would follow him to Florida.

Oh, one other thing.

Joe McEwing, the White Sox’s 38-year-old Triple-A manager, is considered a top managerial prospect. He started his career playing for La Russa in 1998 and ’99, and La Russa remains a huge supporter. He probably will be a big-league coach next year, most likely La Russa’s bench coach. In Chicago.

A move to the White Sox would allow La Russa to retire as baseball’s second-winningest manager all time, and after a couple of years, he could turn his U.S. Cellular Field office over to McEwing, moving upstairs to become team president.

Then again, maybe La Russa’s Cardinals will meet Guillen’s White Sox in the World Series, thanks to clutch pitching by Jackson and Frasor. It’s a crazy world, isn’t it?