Chicago ? So there it was, the classic showdown for which baseball fans had been waiting, Roger Clemens in a bid for his 300th victory, facing down 500-home-run-hitter Sammy Sosa in one of the oldest and most pristine ballparks in America.

And sharing the television screen was an advertisement for the All-Star Game on Fox Sports.

Before Saturday’s game was over, the popular promotional tool, a six-foot rectangular electronic monitor affixed to the brick wall behind and just to the left of home plate, transmitted a variety of advertising and network programming to the television audience.

Fans at Wrigley Field saw only the blank green screen.

Used at ballparks for major telecasts in both the season and playoffs for the last two years, it was a natural for Fox Saturday.

A similar screen will be present tonight during ESPN’s telecast.

But it still was something of a jarring sight at Wrigley, perhaps the most unspoiled stadium in baseball as it is virtually devoid of advertising around the playing field.

“We’re just trying to partner with (Major League Baseball) and we know that this is a mega event,” said John McDonough, Cubs vice president of marketing and broadcasting. “This is not something we requested or encouraged. But seeing that it came from Major League Baseball and it was important to them, we were going to comply with it.”

Both the Fox and ESPN telecasts were to be sent to an unprecedented 90 percent of the country and producers on both networks said the product placement and advertising revenue is too valuable to pass up.

“It’s instead of the rotating sign at NBA games (at the scorer’s tables) or permanent signage,” said Michael Weisman, Fox coordinating producer for baseball. “It’s the wave of the future, frankly.”