One potential reason for GSK's sluggish Breo and Anoro sales

GlaxoSmithKline's ($GSK) respiratory newcomers--and blockbuster hopefuls--Breo and Anoro got off to a slower start than analysts expected. That was a problem for the drugmaker, which was counting on them to make up for plummeting sales of Advair, as pricing pressure in the U.S. and generics in Europe took their toll on the behemoth med.

Some of Glaxo's critics had their own ideas about why the drugs faltered. They pointed to the drugmaker's new sales model, which involved shifting the focus and compensation practices of its field force away from individual quotas and toward doctor-rep interactions. Without those quotas, reps could be missing part of their motivation to go the extra mile, they claimed.

GSK, though, has defended the switch, and analysts have suggested that lower-than-ideal coverage may instead be to blame. Heading into 2016, though, Glaxo says it'll have its best coverage ever for the respiratory pair. More