Kolb signed with the Bills' this offseason. (USATSI)
Bills quarterback Kevin Kolb left Saturday's game against the Redskins with concussion-like symptoms, and a day later, there are concerns that this latest injury could have lasting effects.

With rookie first-round pick E.J. Manuel sidelined for the rest of the preseason with a minor knee injury, the Bills were down to one quarterback on the active roster -- rookie undrafted free agent Jeff Tuel. It's why they signed journeyman Matt Leinart earlier Sunday. And concerns about Kolb's long-term health could explain why the team traded for another backup quarterback, Thaddeus Lewis, who started one game with the Browns in 2012 and was on the Lions' roster this preseason.

"I'm not going to sit here and say everything is fine and dandy; it's a concern," coach Doug Marrone said Saturday of the quarterback situation. Still, the hope is that Manuel will be ready for the regular-season opener against the Patriots.

“That's what I'm hoping for,” Marrone said, according to the team's web site. “[Manuel] had the procedure done and he was with us on the field the other day just watching and observing. I think we just have to wait until that period where the doctor looks at him and says, ‘Here's where we are.' Because people recover so differently from minor stuff.”

If Manuel's available it's reasonable to assume he'll win the starting job by default; if he can't go, however, Tuel would appear to be the next in line with Leinart and Lewis adding depth behind him.

Kolb, meanwhile, arrived in Buffalo after two forgettable seasons in Arizona, where the Cardinals had hoped that he would be their franchise quarterback. Instead, he battled various injuries -- including a concussion -- and only played in 15 games over two years.