This man could be the next CEO of Apple

Apple (AAPL) CEO Tim Cook didn't stray far from his own image on Thursday when he promoted Jeff Williams to be his top lieutenant. The newly named chief operating officer has been called "Tim's Cook Tim Cook" and even a clone of Cook.

"Jeff is hands-down the best operations executive I’ve ever worked with," Cook said in a statement announcing the move along with several other promotions and executive changes.

Both men trained as engineers, got business degrees from Duke University, spent time early in their careers at IBM (IBM) and then joined Apple on the operations and manufacturing side. Both men are also known for their sharp memories, attention to detail -- and height.

But the analogy only goes so far. Cook can get so wrapped up in details that he starts spouting business school jargon like "customer sat" and "marcom," while Williams is more of a down-to-earth speaker. And unlike Cook's whirlwind of public appearances (he's showed up at everywhere from George Washington University's commencement to a digital civil liberties conference this year), Williams had been keeping a low public profile at Apple, at least until recently. A coveted keynote slot at Apple's March product unveiling was Williams' first major appearance at that level.

The move to promote Williams comes as Apple faces some of its biggest challenges yet. Analysts are increasingly worried that global iPhone sales, the engine of the company's revenue and profit growth, may shrink next year for the first time. And while sales of the new Apple watch remain small, the company is likely heading into a much riskier and more complicated area next as it ramps development of its own car. (Williams was one of the first Apple execs to publicly acknowledge the company's interest in the automotive world back at an appearance in May.)

At the same time, Apple's stock price has stagnated, trading at nearly the same price as a year ago. Some investors want to see the company move more quickly into new areas, while others want Apple to use more of its cash hoard to buy back stock and pay dividends.

Amid the tumult, Williams becomes Apple's first COO since Cook left the role in 2011 when he took over for Steve Jobs as CEO. Jobs appointed Cook as COO in 2007.

"Williams will be Cook's right hand man going into this critical transformational period for Apple," says Daniel Ives, senior analyst at FBR Capital Markets. "The COO vacancy needed to be filled with the right fit and Williams has a ton of respect within Cupertino as well as in the technology community."

Williams, who officially heads Apple's manufacturing and operations, has garnered an increasing workload in recent years. Cook put him atop the company's watch effort, the highest-profile new product from Apple since the death of Jobs. He's also overseeing ResearchKit, Apple's ambitious attempt to lure medical researchers to write more apps and perform studies with data collected on Apple devices.

Cook's reliance on Williams has been rewarded time and again. Williams was dispatched to China to help address criticism of worker conditions there, successfully oversaw the integration of numerous key acquisitions and has kept Apple's outsourced, Asian iPhone supply chain in order despite massive growth.

Still, Apple's manufacturing record under Williams is not completely unblemished. Apple struggled to meet initial orders for the watch last year amid problems with a key malfunctioning part. And when Apple supplier GT Advanced went bankrupt, some of the company's creditors blamed Apple and argued that Williams was the "hands on" manager of the relationship.

Williams has an undergraduate degree in mechanical engineering from North Carolina State University to go along with his Duke MBA. After a 13-year stint at IBM, he joined Apple in 1998 as head of worldwide procurement and was promoted to vice president of operations in 2004. In 2010, he was put in charge of Apple's entire supply chain and support units.

Out of the office, Williams is known as an avid cyclist (again, like his boss) who avoids many of the trappings of wealth. He supposedly drives a beat-up Toyota Camry, much to the chagrin of design chief Jony Ive, the New Yorker magazine reported this year. But for Apple investors, Williams' efforts have been almost entirely pleasing.