Berkshire owns 27 percent of the food and beverage giant, with the stake worth about $14 billion as of Thursday's close. A 28 percent slide for Kraft Heinz shares Friday morning, however, cost Berkshire about $3.9 billion.

That's because the earnings outlook for the Warren Buffett -owned company just took a big hit courtesy of problems at Kraft Heinz , one of the crown jewels in the Oracle of Omaha's investing empire. Berkshire investors get the opportunity in the next couple of days to hear Buffett discuss the state of the company both from his letter and in a CNBC interview Monday.

The release of Warren Buffett's annual letter is clouded this year as investors confront an unpleasant last-minute surprise.

Analyst Jay Gelb at Barclays on Friday sliced his earnings per share estimates in half for Berkshire Hathaway, anticipating that Kraft Heinz's move to slash its dividend, along with the disclosure that it has come under regulatory scrutiny, will pose substantial problems.

Gelb cut his Berkshire A shares fourth-quarter EPS estimate to $1,726 from $3,522, and to $1.15 from $2.35 for the B shares. Berkshire is set to release those fourth-quarter earnings on Saturday.

The issues with Kraft Heinz aren't the only problems Berkshire faces. Last year was a tough one for insurers, and the conglomerate could feel some bite.

"The most recent quarter also included substantial catastrophe losses for the global [property and casualty] insurance industry" due to Hurricane Michael and wildfires in California "which we would also expect to negatively impact Berkshire's earnings," Gelb wrote.

For the full year, Gelb took down his earnings estimates to $13,316.88 from $15,112.15 for A shares and to $8.88 from $10.07 for B shares, both representing a 12 percent cut.

Despite earnings issues, the analyst kept his price target for both classes, which he sees as $375,000 and $250 respectively. The targets represent 21.8 percent upside for both shares from Thursday's close.

Kraft Heinz saw its shares tumble after the company said it was lowering its dividend to 40 cents a share, a 36 percent reduction, and said it had received a subpoena from the Securities and Exchange Commission regarding procurement accounting policies.

That came on top of earnings and revenues that missed Wall Street estimates.

Gelb said he expects Buffett to address a number of topics this weekend, including plans for his succession, what the company will do with its more than $80 billion cash stockpile, the possibility of share buybacks, his views on global issues, and the state of the BNSF railroad and the company's energy investments.

—CNBC's Michael Bloom contributed to this report.