Ford executives

There's little question that bringing Alan Mulally on board at Ford was the smartest move the company made in decades, nor is there much debate that credit for the company's salvation is largely due to his office. But could his number be up?

Having joined Ford in 2006 as an outsider from aerospace giant Boeing, Mulally (pictured above, left) has been on the job for over five years now. And while he's showing no signs of slowing down, sources indicate he is unlikely to stay on the job beyond another year or two.

The question, then, is who might replace him. Citing internal sources, The Wall Street Journal recently reported that Ford has begun putting together a short-list with four candidates: two internal and two external. However, TheDetroitBureau.com has offered a rebuttal saying that the Blue Oval denies beginning such a search.

Either way, at some point, a search will need to begin. Mulally's case notwithstanding, cases of successful hires from outside the business to the top of a major automaker like Ford have been few and far between, but the company could be forced by shareholders to consider outside candidates as well as internal promotions.

The list, according to the WSJ, currently includes Mark Fields (pictured above at right), currently Ford's President of the Americas; Joe Hinrichs (second from right), head of Ford's Asian operations; John Krafcik, a former Ford engineer who now runs Hyundai in America; and Phil Martens, Ford's former product development chief who now runs aluminum manufacturer Novelis.

Again, for its part, Ford denies that it has begun searching for Mulally's successor, but prudent management could very well dictate that it must begin looking – whether the much-lauded executive is ready to retire or not.