Greg Abel's challenge: Lead Berkshire into a new era without the Buffett touch

For the first time in decades, Berkshire Hathaway is getting a new chief executive

- Karen Langley, Nicole Friedman & Gregory Zuckerman

Warren Buffett has done what he can to prepare his successor at Berkshire Hathaway.

He has tasked CEO-in-waiting Greg Abel with running most of the companies the sprawling conglomerate owns.

He named Abel a vice chairman, worked with him on recent investments in Japan and shared the stage with him at Berkshire's famous annual meetings.

There is one thing he can't simply hand off to the next guy: the Buffett brand and the glow it imbues on anything his company touches.

Buffett said Saturday at Berkshire's annual meeting that he plans to step down as CEO at the end of the year and hand the reins to Abel.

In his 60 years of delivering stunning investment returns and folksy wisdom, the 94-year-old has been the glue that binds together Berkshire's collection of businesses—from Dairy Queen and Duracell to railways and insurers—at a time when big conglomerates are out of style.

Abel will inherit the challenge of overseeing that wide-ranging empire, while living up to Buffett's seemingly impossible-to-replicate record in stock picking—something even Buffett has struggled to do in recent years.

"He would make a huge mistake trying to be Warren Buffett, and he knows that," said Will Danoff, the Fidelity money manager who counts Berkshire as a top holding.

"Shareholders want Greg to be the best Greg Abel he can be."

Buffett isn't just an investor.

His unique stature allows him to confer legitimacy on damaged businesses in times of crisis—as he famously did when Wall Street veered toward potential collapse—and to extract a good deal for his shareholders in the process.

And his reputation as a brilliant investor means that many shareholders are content letting Berkshire amass a huge pile of cash, because they expect that Buffett will eventually be able to deploy it well.

No one can completely fill those shoes.

"Warren's so unique," Bill Gates, the Microsoft co-founder, said of his close friend.