Leerink analyst David Larsen notes that The Wall Street Journal reported that Walgreens (WBA) has approached AmerisourceBergen (ABC) about a potential takeover. The analyst is surprised that talks of such a large transaction have surfaced so quickly following the Rite Aid (RAD) deal, but says he has always believed that Walgreens at some point would seek to acquire either Express Scripts (ESRX) or AmerisourceBergen. Given the broad-based speculation in the business press about this deal, it is possible shares of Express Scripts will trade off, Larsen contends.