UnitedHealth Sniffles

Borsch points to a deteriorating cash flow metric as well. Specifically, he notes, the company's ratio of cash flow to net income -- which tends to handily exceed 100% -- fell to 95% in the latest quarter.

Going forward, Borsch sees other challenges looming. He points out that UnitedHealth has pursued numerous acquisitions over the past couple of years and warns that integrations risks -- beyond those anticipated by Wall Street -- remain.

Indeed, his latest report suggests, UnitedHealth has already started to suffer some growth-related pains.

"For the first time that we're aware of, multiple competitors to UnitedHealth are pointing to marketplace 'noise' suggesting that service levels at UNH may have slipped or be slipping," Borsch writes. "While it remains unclear if the alleged service issues will prove to be a 'bump in the road' or something deeper, we surmise they may reflect the unavoidable strain from UNH integration of multiple large-scale acquisitions coupled with the task of servicing more than 4 million new AARP-UNH Medicare drug plan members."

In the meantime, Borsch notes, United Health has found itself saddled with a poor corporate governance rating from Institutional Shareholder Services. Specifically, he says, the company scored in the bottom quintile of large-cap managed-care players in the latest ISS study.

UnitedHealth fell short on some compensation matters in particular. The company has, by now, become well known for handsomely rewarding its executives.

UnitedHealth CEO William McGuire raked in $7.7 million worth of salary and bonuses last year. Perhaps more noteworthy, however, McGuire has since gone on to cash in 2.3 million stock options -- worth a whopping $125 million -- since that time.

Ongoing Challenges

Still, even Borsch foresees no "collapse" in the company's earnings.

Rather, he predicts an inevitable slowdown in profit growth that will lead to a contraction in the company's price-to-earnings ratio. And he warns investors against counting on Medicare -- which is undergoing its biggest expansion in history -- to bail out the company.