ORCHARD PARK, N.Y. (AP) -- Bills coach Doug Marrone repeated the word ''challenging'' three times on Wednesday when addressing the possibility of losing yet another quarterback to injury.
That's the reality Marrone is faced with after listing interim starter Thad Lewis as being ''50-50'' because of bruised ribs.
The injury opens the possibility of undrafted rookie Jeff Tuel or newly signed free-agent Matt Flynn starting on Sunday, when the Bills (3-5) host the unbeaten and defensively stingy Kansas City Chiefs (8-0).
''Challenging, challenging, challenging is the word we use,'' Marrone said. ''We'll do whatever we can if we have to go with either Jeff or Matt and do the best job for them in putting them in a position to win for the team.''
With rookie starter EJ Manuel (sprained right knee) still not cleared to play, and veteran backup Kevin Kolb (concussion) out for the season, the Bills could be down to their fourth-string quarterback after Lewis was hurt in a 35-17 loss at New Orleans last weekend.
Making his third consecutive start since being promoted off the practice squad, Lewis was initially injured on the first play from scrimmage, when linebacker David Hawthorne struck the quarterback with a helmet-first hit into his right ribs. Lewis fumbled the ball and had difficulty getting off the field before returning for the next series and completing the game.
''Thad is truly, right now, 50-50,'' Marrone said, adding tests on Lewis' ribs came back negative.
Lewis has gone 1-2 as a starter since Manuel was hurt in a 37-24 loss at Cleveland on Oct. 3. Lewis has put up respectable numbers in Buffalo, in completing 62 of 103 passes for 652 yards, with three touchdowns and two interceptions.
Manuel practiced for the first time on Wednesday, but has already been ruled out from playing.
The Bills' offense could be depleted further with running back C.J. Spiller limited by a sprained left ankle and leading receiver Stevie Johnson bothered by a hip injury.
Tuel and Flynn split first-team reps in preparing for the possibility of facing a Chiefs defense that has yet to allow more than 17 points in a game this season, and leads the league with 36 sacks and is second with 20 takeaways.
Tuel, out of Washington State, showed he wasn't ready to play at the NFL level in replacing Manuel against Cleveland. Tuel finished 8 of 20 for 80 yards, and threw an interception that was returned for a game-sealing touchdown in the final two minutes.
''I learned a lot from Cleveland and I feel like I've been getting better,'' Tuel said. ''I had a lot of adrenalin flowing, got the nerves and all that, so I know how to handle it and prepare for it.''
Flynn, in his sixth NFL season, has more experience but has had difficulty holding on to a job. After spending his first four seasons as Aaron Rodgers' backup in Green Bay, Flynn is on his third team in less than a year.
Traded by Seattle to Oakland this offseason, Flynn lost the starting job to Terrelle Pryor before being cut by the Raiders on Oct. 7. He signed with Buffalo a week later, when the Bills were scrambling to address their lack of experienced depth at quarterback.
Flynn has had little time to become familiar with the Bills offense and their receivers. The practice time Flynn enjoyed Wednesday was the most since his arrival.
''I feel better about Jeff right now, because I know Jeff,'' Marrone said. ''That's not to say Matt's not good enough. I just haven't seen enough of Matt to really say it's a competition, yet.''
Flynn understands the position he's in, while maintaining confidence in his abilities.
''I'm not going to let whatever happened in my past affect how I go about my business, how I go about playing the game,'' Flynn said. ''I've got a lot of confidence in myself. Call it stubbornness or competitiveness or whatever you want to call it, I've always believed in what I can do.''
Veteran running back Fred Jackson acknowledged another switch at quarterback could be troublesome.
''When you don't have consistency at a spot like that, it makes it tough,'' Jackson said. ''But we've had guys come in here and step up and give us an opportunity to win football games. And that's all we can ask of them to do. And whoever it is this weekend, that's what we'll do.''
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