A Nissan spokesman declined comment.
Mr. McNabb, 47, senior VP-sales and marketing for the Nissan and Infiniti brands, is believed to be moving to an undisclosed Detroit carmaker; he had faced aggressive and unrealistic sales targets from his superiors at Nissan, the executive said.
Nissan has suffered from an executive exodus at all levels since it relocated its headquarters to Nashville, Tenn., from Southern California in 2006.
Mr. McNabb was a rising star at Nissan, having first joined the automaker in 1986. But in fall 2005, shortly after being promoted to a global position in Japan at parent Nissan Motor Co. (VP-sales and marketing for general overseas marketing for all markets except North America and Europe), he resigned and within months joined Mercedes-Benz USA as VP-marketing.
Mercedes-Benz moved him to VP-sales in January 2007. But Mr. McNabb suddenly split in March of that year to rejoin Nissan as the corporate VP, heading the Infiniti brand's global business. He was promoted three months later to his current position, retaining the global Infiniti title and duties.
Nissan and Infiniti spend about $1 billion in U.S. media annually. The automaker's U.S. vehicle sales rose by 4.8% last year to nearly 1.07 million vehicles vs. 2006, according to Automotive News. The company's vehicle sales in the first two months of 2008 are flat at 162,824 units vs. 167,862 for the year-ago period.