His ad career started in 1999 at Y&R Advertising, New York. Two years later , while Mr. Nelson was at a boutique, a headhunter called with a job on Microsoft Corp.'s Xbox and PC games. An avid gamer, Mr. Nelson met with now-boss Suresh Nair, exec VP-director of planning at Interpublic Group of Cos.' McCann-Erickson Worldwide. He was impressed: "We look for that secret sauce," Mr. Nair says of prospective hires. Mr. Nelson joined McCann in late 2001, and at 29, now leads efforts on a global account.