(Bloomberg Businessweek) -- When Apple announced the pending departure of Chief Design Officer Jony Ive last month, it threw the spotlight on an executive few outsiders know: Chief Operating Officer Jeff Williams, who has now also taken over the company’s legendary design studio. This added fiefdom makes Williams unambiguously the second-most important person at Apple and Tim Cook’s heir apparent as CEO. And he’s very much in the mold of the current chief executive: a paragon of operational efficiency and even temper not prone to quite the same highs and lows of Cook’s more visionary predecessor, Steve Jobs.

Several current and former colleagues, who spoke on the condition of anonymity because they weren’t authorized to speak publicly, say that during his years as the company’s operations chief, Cook’s old job, Williams has distinguished himself as a modest, disciplined, demanding leader in the current CEO’s style. He’s negotiated with suppliers, shipped hundreds of millions of devices a year from Chinese factories to the rest of the globe, and been a bit more hands-on with product development than Cook, they say. Williams attends weekly reviews of product and industrial design progress, subsequently briefing Cook for a final signoff, and has been the lead executive shepherding the Apple Watch to market. Within Apple, Williams is broadly regarded as a strong choice for the top job, and current and former colleagues say management had been steadily positioning him as such long before Ive’s departure.

Williams’s elevation has also heightened worries about the company’s ability to jolt itself out of a perceived complacency. Under Cook’s tenure, Apple has more than doubled its market value, briefly pushing it above US$1 trillion, and sold hundreds of millions of customers more expensive lines of iPhones and iPads, wireless AirPods, and subscription services like Apple Music. Yet after a period of astonishing sales growth, unit sales of the iPhone, which have long accounted for about two-thirds of Apple’s revenue, have been largely flat for years, and the company has struggled to compete in fast-growing markets such as China and India.

Since its rescue from the brink of bankruptcy in the late 1990s, Apple has prided itself on making pricey products into mainstream hits on the strength of its design, and the design team has long been the center of its corporate culture. But Ive was seen by many as the last Jobs-level product genius with executive clout. As Cook approaches his eighth anniversary as Apple’s CEO, the operations team has solidified its influence over product development. Cook doesn’t appear to be on his way out in the near future, and Williams’s move into the on-deck circle represents a long-term bet on that model, according to current and former employees. “Jeff is 95 per cent operations and 5 per cent product,” says someone who knows him. “Apple has become an operations company.”

“One doesn’t necessarily need a visionary as CEO of Apple as long as there’s a visionary in the company that the CEO can work with,” says Michael Gartenberg, a former Apple marketing executive. “Tim Cook had Jony Ive. The question is, with Ive gone, who is the visionary at the company that can guide the next big thing?” Apple declined to comment or make Williams available for an interview.

Like Cook, Williams grew up in the American South, got an MBA from Duke, and spent years at IBM before joining Apple in the late 1990s. He started in 1998 as a procurement manager, negotiating with component suppliers, and worked his way up to Jobs’s executive team in 2010 as senior vice president of operations. Under Cook, he became known for carrying a massive binder of data on product development and operations plans that he could quickly reference to answer the CEO’s questions during meetings, often while clad, like his boss, in a uniform of jeans and an untucked dress shirt. Williams also has often relied in meetings on a pocket-size notebook, and colleagues say they make sure to follow up on any part of the conversation they see him write down.

Williams took over leadership of the Apple Watch development team in 2013 after pitching the smartwatch’s use as a health tool, and spoke for the first time at a product launch in 2015, announcing the company’s health research efforts. Since his appointment as COO later that year, he’s announced each subsequent version of the smartwatch, cut the ribbon on a nine-figure investment in Kentucky glassmaker Corning next to Senate Majority Leader Mitch McConnell, and taken on more responsibility in Apple’s day-to-day product development.

In his current role, Williams’s responsibilities ranged widely even before he took over the company’s hardware and software design groups. Besides managing the Apple Watch, he oversees the entire supply chain, materials sourcing, fitness and health research and app development, AppleCare customer support, and some of the finance teams. The COO, also like his boss, has a knack for watching, listening, and asking sharp questions. A former Apple executive says Williams has made an effort to speak the same language as the company’s engineers, though he can be self-deprecating about his technical expertise.

Williams is a hiking and biking aficionado who’s known to arrive at work before 7 a.m. and stay late into the evening, often cycling between meetings. He has a reputation as an even-keeled, even soft-spoken presence. “Sometimes there will be a conference call, Jeff will be on it, but nobody knew until he chimed in halfway through,” says someone who’s worked with him. While Williams can be direct and demanding in meetings with other executives, current and former colleagues say he sometimes relies heavily on a circle of lieutenants to play bad cop in larger engineering-team meetings. With the designers, his sensibility doesn’t always translate. “He comes from the operations side, and the metrics being applied there often have very little meaning in design,” says a longtime member of the design team.

The Watch has been Williams’s biggest test. Months before the first model’s release in 2015, some employees testing the device began having allergic reactions to the type of nickel used in its casing, a not-uncommon issue with wristwear. Williams made the call to scrap thousands of Watches the company had already produced and ramp up a separate manufacturing line with a different kind of nickel. Employees also noticed that the “taptic engine,” a Williams priority that allows the Watch to vibrate more quietly than a typical phone part when it receives notifications, was prone to long-term failure from corrosion. Again, Williams decided not to send out a few thousand Watches that were affected. Employees got them instead.

These choices spared many early adopters from getting defective early models of the Apple Watch. They also helped make the watch tough to find in stores for months after its official release, and some online shipments were delayed, too. When customers could find some, they might be the Watch models shipped with 18-karat gold cases, which cost as much as US$17,000—conceivable for wealthy Rolex fans, but a poor investment given that Apple’s model would be obsolete in a few years.

The Apple Watch wasn’t an immediate hit on the level of the iPhone or even the iPad, and the first model was sluggish and lacked must-have apps. The company discontinued the exorbitant gold versions after a year; it sold in the low tens of thousands of them, but few after the first two weeks. Still, as the Watch’s hardware and software have improved, Apple has quietly taken control of the market for internet-connected fitness wristbands, accounting for more than half the sales in the category last year, according to researcher Strategy Analytics.

Williams now oversees the development of all Apple hardware products, holding weekly meetings to gauge their progress. Although the process is formally called NPR, or New Product Review, some employees call this the “Jeff Review.” During the development of the AirPods, some of them noticed that Williams continued wearing Apple’s wired headphones instead of the new product. Williams wasn’t yet happy with the fit of the wireless model.

People close to the design team say they trust Williams to understand the value of what they do and help implement their ideas instead of overruling them. In addition to his experience with the Apple Watch, Williams briefly oversaw Apple’s mobile device engineering team a decade ago, during the months between the departure of iPod co-creator Tony Fadell and the end of a noncompete agreement for Fadell’s replacement, former IBM executive Mark Papermaster.

One former senior Apple executive says he’s less worried about Williams’s ability to implement ideas from the design team than he is about the managers reporting to Williams. The new team leaders, longtime Apple hardware and software design managers Evans Hankey and Alan Dye, are a “step down” from Ive in terms of design prowess, the former senior executive says, but acknowledges that workflow may be simpler with Hankey and Dye running things. Before, “those people were pseudo in charge, but not really in charge, because Jony could overrule them.”

Outside Apple, Williams occasionally ventures to his family’s beach house in Aptos, Calif., a 45-minute drive from the company’s headquarters, or appears at a San Francisco gala with his wife, Melissa. For shareholders worried about the future, Williams’s somewhat quiet public persona and lack of design intuition may not inspire much excitement. Cook’s inner circle includes a handful of other Jobs buddies with more extensive product track records, including marketing chief Phil Schiller and services head Eddy Cue. But they’re all about Williams’s age, and he’s 56—just three years younger than Cook.

“He’s the closest thing at the company to Tim Cook, and you’ll get more of that,” a former senior Apple executive says of Williams. “If you think Cook is doing a good job, then it’s a good choice.”