Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.

While the "vote of confidence" from Buffett's investment validates the long-term value of UnitedHealth shares, the "management needs to regain trust and credibility with investors, and get back to its beat and raise reputation of the past," said James Harlow, senior vice president at Novare Capital Management.

Unsurprisingly, the options pits are seeing ample activity. So far 377,000 calls and 121,000 puts have been exchanged so far, 6 times the average daily pace. Most popular are the expiring August 300, 305, and 310 calls, where new positions are being opened.