Goldman Sachs just signaled a terrifying turning point for Nike (NKE)

Goldman Sachs investment services downgraded Nike to a neutral rating.
The bank cited "fundamental challenges" and an excess of inventory in its note to investors.
The bad news for Nike indicates the company has not managed to turn around its business yet.
Nike is still facing headwinds as it seeks to right the ship.
Citing "fundamental challenges" in the industry, slowing sales, and an excess of inventory with retail partners, Goldman Sachs downgraded Nike to a "neutral rating" in a note