JPMorgan analyst Gary Taylor views Cigna's (CI) acquisition of Express Scripts (ESRX), which drove an 11.5% pullback in the shares yesterday, as a "primarily defensive deal, possibly rushed, reflecting a fairly sizable strategic turn for both companies." The analyst says that barring a complete collapse of pharmacy benefit manager or health plan margins over the next few years, he can make a "substantial upside case" for the shares of Cigna. The "sizable" free cash flow generation potential of the company is likely being underappreciated, Taylor tells investors in a research note. He keeps an Overweight rating on Cigna.