Brian McCarthy, a spokesman for the N.F.L., said: “We felt it was unfair to single out a particular sport. Concussions aren’t just a football issue.”

The N.F.L. is correct that concussions are an issue in other sports. According to researchers at Nationwide Children’s Hospital in Columbus, Ohio, high school football players report about 100,000 concussions per year. The second through ninth-ranked sports combined reach 110,000.

The demand was evidence of the N.F.L.’s delicate dance regarding head injuries, as well as its power to shape its public image. The league has responded to well-publicized links between football and brain damage by producing a public service announcement about concussions, fining players for helmet-to-helmet hits and pushing for changes to state laws covering youth sports. At the same time, its business depends on people watching the sport and approving of their children playing it.

Toyota is not an official sponsor of the N.F.L., but it advertises with individual teams and buys commercial time on network game broadcasts.

Advertising executives described the N.F.L.’s action, reported by Reuters on Wednesday, as extraordinarily unusual. The ad was produced and subsequently edited by the Saatchi & Saatchi agency.

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“It’s not unheard for a spot to be changed after launch, but it’s usually after a portion of the public takes offense to something in it,” said Mark DiMassimo, chief creative officer for DiGo, a New York-based advertising agency.

The football commercial was one installment of Toyota’s “Ideas for Life” campaign depicting how Toyota’s automobile safety research could apply to other fields.

Ziegler, the Toyota spokeswoman, said that the edited commercial was scheduled to run through this week, but that she was unsure whether it would run during one of Sunday’s conference championship games. She added that Toyota had already planned not to advertise during the Super Bowl on Feb. 6 because it is not unveiling a new vehicle.

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McCarthy, the league spokesman, said the N.F.L. also had Toyota “tone down the crunching,” which he described as sounds Saatchi & Saatchi had manufactured and dubbed to enhance the footage of colliding players.

“You wouldn’t hear that on a football field,” McCarthy said.

The collision in the commercial would almost certainly have been considered legal on an N.F.L. — and high school — field. Players are generally penalized for hitting the heads only of defenseless players, such as a quarterback throwing or a receiver in the process of making a catch.

After several high-profile incidents last October, Commissioner Roger Goodell began fining players up to $100,000 for such infractions, regardless of whether they were flagged by an official.

The tackle in the Toyota ad is not perfectly clear but resembles a typical runner and tackler making relatively routine, though dangerous, contact.

The N.F.L. recently had its officiating department watch every game and, whether or not the play drew a flag, keep a log of every play that violated a safety-related rule. The league then sends the list to its own media entities, like NFL Films and NFL Network, as well as advertisers, with the understanding that those plays may not be used in commercials or other promotional materials.

The Toyota ad, McCarthy said, “was clearly showing helmet-to-helmet impact that we feel is not necessary to show in an automobile ad. It’s not representing the image we want to have portrayed.”