Most companies that ran ads during the Super Bowl on Feb. 2 shelled out roughly $4 million for 30 seconds of ad time, which sold out in December.

But not Subway, the sandwich chain owned by Doctor's Associates Inc. Tony Pace, Subway's chief marketing officer, held off buying and was able to purchase a slot the Friday before the game, after an advertiser dropped out.

Not only did Mr. Pace get good positioning for his ad—in the second quarter of the game, well before the lopsided score prompted the record viewership to tail off a bit—he also says he paid less than the going rate, though he won't say how much.

It was a move that reflected Mr. Pace's emphasis on being nimble and keeping ahead of the competition. It's a big task in the fast-food business, which is littered with massive ad budgets, bruising price wars and copycat marketing.

On top of those challenges, Mr. Pace has to juggle the many marketing channels that have emerged in recent years, from Facebook to Pinterest, and craft campaigns that suit the vagaries of tablets and smartphones.