Anthem seemed to be "the most likely" bidder, but Cigna and Aetna would make sense, as well, said Tom Carroll, managing director at Stifel Nicolaus. Carroll expects "a wave of consolidation" in the health-care sector.
"Our view was that Anthem and Aetna are both in a position where they must own Humana to maintain relevance long term," Carroll said in a CNBC "Closing Bell" interview.
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Humana has emerged as "the big-ticket player" in Medicare, the federal program for older Americans, Carroll said. The company gets most of its sales from patients on the plan, which puts it in a key market position.
Carroll added that Humana will likely be a beneficiary of a changing Medicare landscape moving forward. Next year, he expects the first positive Medicare Advantage rate growth in about five years.
He partially attributed the rate trends to the Affordable Care Act, a key policy of President Barack Obama's administration. The ACA has boosted Humana's potential customer pool, as it requires Americans to have health insurance.
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Before Friday's trading, Anthem could have fetched a price of at least $230 per share, Carroll noted. After its 19 percent jump, the shares were trading around $212.
Humana reported $34 billion in revenue last year. In the first quarter, its membership climbed to 14.2 million customers.
Humana, Anthem and Cigna did not immediately responded to requests for comment from CNBC. Aetna declined to comment.
Read the full Wall Street Journal report here.