And then there were two, if recent reports are to be believed. Ford CEO Alan Mulally and Microsoft Executive Vice President Satya Nadella are apparently the top two candidates for the CEO job at Microsoft, with two wild cards, Tony Bates and Stephen Elop, remaining as only distant possibilities for the post.

The report of the narrowed CEO search decision comes from Bloomberg, which has been reliable and credible in the past. The report cites unnamed Microsoft insiders as stating that Mr. Nadella, who currently oversees the firm's cloud and enterprises business, and turnaround guru Mulally have risen to the top after months of search efforts.

There's just one problem: They couldn't be more different.

A former Boeing executive, Mr. Mulally was famously asked to run Ford when William Clay Ford, Jr. determined he was unable to lead the car maker into its next growth phase. At the time, the decision was criticized because Mr. Mulally had no auto industry background, but Ford's subsequent dramatic turnaround—it was the only US automaker that didn't need federal assistance during the automotive industry crisis of 2008—and Mulally's decisive moves end any criticism.

Mr. Nadella, meanwhile, is in many ways the ultimate Microsoft insider. With the firm since 1992, he led Microsoft's $19 billion Server and Tools business, architecting its seamless transition from on-premises server solutions to cloud computing.

The attraction to Mr. Mulally is obvious: Though he is a tech industry outsider, he previously turned around a business in which he was also initially an outsider. But he's also likely to be a short-timer: At the age of 68, he'd been planning to retire from Ford in 2014. And Ford resolutely claims he's unavailable. "Alan remains completely focused on executing our One Ford plan," a Ford statement notes. "We do not engage in speculation."

Nadella is well respected within Microsoft, and of course the business he led could serve as a model for the rest of Microsoft. But there is a growing worry that Microsoft needs real change, and that that change cannot come from someone who endured the endless internal politics of the past 20 years at the firm.

Of course, Microsoft's CEO role is complex, and finding a single candidate who can understand and speak fluently about the company's many divergent product lines is a difficult task. Microsoft's board of directors met two weeks ago to discuss its progress in finding a new CEO and although it originally hoped to be able to announce its decision this year, the board is now expected to push that back to early 2014.

The next CEO must have an "extensive track record in managing complex, global organizations within a fast-paced and highly competitive market sector [and a] track record of delivering top- and bottom-line results," internal documents obtained by Bloomberg note. "[He or she must have the] proven ability to lead a multi-billion dollar organization and large employee base."

As for Tony Bates and Stephen Elop, the two erstwhile Microsoft executives—Bates came to Microsoft with Skype, and Elop is set to return to the firm when it concludes its purchase of Nokia's devices and services businesses—they remain long shots.

But Mr. Bates is apparently a favorite of Microsoft's employees, according to a report in All Things D. He's seen as the right combination of insider and outsider, and because of his extensive Silicon Valley experience, his rise to CEO could signal a new era of cooperation between Microsoft and its competitors and partners. That view ignores the hard reality that Microsoft's integration of Skype technology into its other products has been downright disastrous. Indeed, though ostensibly a part of Microsoft, Skype appears to be run as an independent business that appears clueless to the needs of customers served by other parts of the company.