Remember back in May, when a start-up called Fantex announced it would sell a "tracking stock" tied to Buffalo Bills quarterback EJ Manuel?

Turns out that stock is having a bad week.

Share prices of the stock, which trades on the company's own secondary market, dropped from $9.60 last Wednesday to $5.00 at Tuesday's last trade, one day after Manuel was benched as the Bills' starter.

The drop in price doesn't impact Manuel, who received $4.97 million up front in exchange for Fantex to take a 10 percent stake in his future income. But investors in the stock have taken a hit, as will Fantex if Manuel's career falters and his income stream dries up.

Fantex struggled to generate interest in Manuel's stock during an initial public offering this summer. The company needed to step in and purchase 250,000 shares (48 percent) of the offering, according to the New York Times. Shares were sold during the IPO at $10 and began trading at $11.50.

Trading volume has been sluggish. The company's website indicates that no trades were executed between last Wednesday and Monday, when Manuel was benched, and that only 24 shares were traded Monday.