“Countdown With Keith Olbermann” the highly rated cable news program, will be shown on network television on Sunday before a preseason NBC football game between the Philadelphia Eagles and the Pittsburgh Steelers. Since Mr. Olbermann, right, will have a regular role in NBC’s football coverage once the season begins — appearing as a co-host on the pregame show “Football Night in America” on Sundays — this weekend’s appearance of his cable show will give a wider audience a look at what he has been up for the last four years. “ ‘Countdown’ is rocketing right now over at MSNBC — its ratings are going through the roof,” said Phil Griffin, senior vice president of NBC News. (In July Mr. Olbermann’s show averaged 721,000 viewers, an increase of 88 percent over last July, according to MSNBC.) Mr. Griffin added, “The world has changed, and I think people have come in line with the smart, focused approach he has on the show.” No immediate plans for additional network appearances of “Countdown” have been made, but Mr. Griffen did not rule them out. “It may be the first of several times you see Olbermann on the network,” he said.