Who's waiting in the wings at Apple?

Could anyone ever replace Steve Jobs? That's the question on manyinvestors' minds as Apple wrestles with yet another medical leavefor the company's chief visionary. Jobs announced Monday thatApple's board had granted him a leave for health reasons, but didnot specify how long he would be gone.

In his place, chief operating officer Tim Cook will again step into run Apple's operations on a "day-to-day" basis. Jobs will retainthe title of CEO and continue to "be involved in major strategicdecisions for the company."

Still, the uncertainty of both the tenure and cause for Jobs'sleave will surely have many taking a closer look at Apple's otherexecutives. While the company is known to have a well-regardedleadership bench, no one is thought to have Jobs's mix of obsessiveattention to detail, negotiating power, inspirational product ideasand legendary Silicon Valley entrepreneur status.

Taken together, the top brass at Apple is likely to keep theplace humming in Jobs's absence, at least in the short term.

Over the long haul, however, Apple observers question whether anyof these leaders has the same capacity to inspire the sort of game-changing technology and design feats for which Jobs is so wellknown. As David Yoffie, a Harvard Business School professor who hasstudied the technology industry and served on tech company boards,told The New York Times: "The company could not thrive if Stevedidn't have an extremely talented team around him. But you can'treplace Steve on some levels."

A few of the key players:

Tim Cook: The IBM and Compaq veteran is considered an operationalwhiz who is as obsessive about running a smooth operation as Jobs isabout perfect products. Cook, an Alabama native, ran the companyduring Jobs's 2004 and 2009 leaves, and is widely regarded to havedone so successfully. Jobs hired him in 1998 to stabilize Apple'soperations woes at one of its darkest hours. Cook responsibilitiesbroadened. He was praised for keeping the trains running duringJobs's 2009 leave, with product developments and launches kept onschedule. Still, some have criticized him for lacking the strategicvision Jobs has. Cook makes CEO-level pay: In 2010, Cook'scompensation was $58 million, including an $800,000 salary, $5million bonus and $52 million in stock awards.

Jonathan Ive: As senior vice president of industrial design, Iveis responsible - second to Jobs, of course - for the look and feelof Apple's products. He has been called Apple's Man Behind theCurtain for his quiet but influential role in executing Jobs'sinspiration; known as being close to Jobs, Ive, a Briton, has been acritical to the company's design process since Apple launched itsbrightly hued iMacs in the late 1990s.

Scott Forstall: As senior vice president of iPhone software,Forstall manages the guts of what is arguably Apple's most popularand revolutionary product. That puts him in a place of increasinginfluence, as software becomes more and more of a distinguishingfactor in Apple's products, according to news reports. The companycredits Forstall, who joined Apple in 1997, with being one of theoriginal architects of the Mac OS X operating system.

Philip Schiller: Apple may be known for its technology, itsdesign and the efficiency of its operations, but the company is alsoa master marketer. Much of that is due to Jobs, of course, long thecompany's key pitchman, but it's also due to Schiller, Apple'ssenior vice president of worldwide product marketing. During Jobs's2009 leave, Schiller took the stage for the MacWorld keynote andproduct launches such as the iPhone 3GS and Macbook Pro models.

Eddy Cue: Vice president of Internet services Cue "is regarded asan all-purpose fixer," according to the Wall Street Journal, "whohas helped Mr. Jobs negotiate tricky relationships with musiccompanies, movie studios and publishers." Cue, whom Fast Companycalled the second-most creative person in business, was a low-levelIT staffer before Jobs returned in the mid-1990s.