In 2009, sales of digital singles eclipsed the 1 billion unit mark, while physical album and single sales continued to decline. With Monday’s digital release of Lil Wayne’s I Am Not A Human Being album, some retailers fear that trend will only grow exponentially. As previously reported, I Am Not A Human Being will not be accompanied by a physical release until Ocober 12.

“Its disturbing,” on un-named merchant told Billboard. “Its definitely putting brick-and-mortar second, and we are going to lose business that we would normally get. How is the consumer going to know that the album will have a second physical release?”

As sales have declined, Lil Wayne’s albums have been one of the few bright spots for physical retailers during the past few years. Tha Carter III was the top-selling album of 2008, registering over 2.8 million copies sold in a span of six months. Despite being panned by critics and being leaked weeks before its physical release, Wayne’s Rock effort, Rebirth enjoyed two successful singles, eventually being ranked number four on Big Champagne’s Ultimate Chart. Digital sales accounted for 17 percent of Tha Carter III sales, while 11 percent of Rebirth‘s total sales were digital.

Billboard cites various sources which estimate Cash Money/Universal Motown projects first week digital sales of 90,000 units for I Am Not A Human Being. The projections for first-week physical sales of the album are currently estimated at 225,000 units. A full breakdown of the projected sales, as well as a comparison to other digital releases is available via Billboard‘s Web site.