Health care investors were blindsided on Thursday afternoon when Dow Jones reported that CVS Health Corp CVS is exploring a $66 billion bid for Aetna Inc AET. As expected, Wall Street analysts have a lot to say about the potential deal. In a new note on Friday, Citigroup analyst Alvin Concepcion said a marriage between CVS and Aetna makes sense in principle as the health care industry prepares for a major new competitor in Amazon.com, Inc. AMZN. “In sum, we see this potential deal as both evolutionary and revolutionary given the dynamic healthcare environment and push toward consumerism coupled with a challenged retail backdrop and the need to combat a looming AMZN threat,” Concepcion said. A $66 billion deal would be a tough pill for the $73 billion CVS to swallow. Read moreSome downside still holds. $CVS, CVS Health Corporation / D The upside looks limited. $AET, Aetna Inc. / D