When Buffalo Bills running back Fred Jackson got hurt in today's 48-28 loss to the New York Jets, it felt like a punch to the gut. The initial diagnosis on Jackson's knee injury, however, is fairly optimistic: he'll have an MRI tomorrow, but for now, it's being called a sprained LCL.

The situation is the polar opposite for David Nelson, whose fourth-quarter knee injury - while nearly as ugly to behold - came in the mind-numbing stretch of game time when Bills fans had largely mentally checked out. According to head coach Chan Gailey, however, there's plenty to worry about regarding Nelson.

"Fred doesn't look as bad as David," Gailey told reporters after the game. "We don't know how bad David is but it doesn't look good right now. Fred doesn't look nearly as bad but we're going to get a further evaluation tomorrow."

A league source tells Mike Florio of Pro Football Talk that the Bills believe Nelson may have a torn ACL.

Losing Nelson for an extended period time would be a crippling blow for a Bills passing attack that is already off to a brutal start. As one of two dependable possession receivers for quarterback Ryan Fitzpatrick, losing Nelson would increase the amount of attention that defenses are paying to tight end Scott Chandler. With problems on the outside opposite the hobbled Stevie Johnson, Fitzpatrick needs as many dependable receivers as he can get.

Nelson, like Jackson, will have an MRI on Monday to determine the full extent of his injury. If the news is bad, the Bills may be looking to make another move at receiver sooner rather than later.