Lewis had only been promoted off Buffalo's practice squad last week to fill in for injured rookie EJ Manuel, who is out indefinitely with a sprained right knee. Manuel was hurt in a 37-24 loss at Cleveland on Oct. 3.
In making a brief visit to the locker room Monday, Manuel walked without a sign of a limp and acknowledged that his knee is feeling better.
Flynn could be the next option for Buffalo. Undrafted rookie Jeff Tuel, the only quarterback on the team's active roster, showed he's not ready after struggling in taking over for Manuel against the Browns. The Bills also signed quarterback Dennis Dixon to their practice squad last week.
A sixth-year player, Flynn was cut by Oakland last week after he failed to win the starting job. Flynn had dropped to third on the Raiders' depth chart behind starter Terrelle Pryor and undrafted free agent Matt McGloin.
Oakland gave up two draft picks to acquire Flynn last offseason in trade with Seattle. The Raiders also reworked Flynn's contract in which the quarterback was guaranteed to be paid $6.5 million this season.
Flynn instead struggled in two appearances. He completed 22 of 34 passes for 246 yards with a touchdown and interception.
Selected in the seventh round of the 2008 draft by Green Bay, Flynn spent his first four seasons as Aaron Rodgers' backup. In 2012, Flynn signed with Seattle, before losing the starting job to rookie Russell Wilson.
Lewis had a solid outing against Cincinnati in only his second career game. He went 19 of 32 for 216 yards passing and threw two fourth-quarter touchdowns including a 40-yarder to Marquise Goodwin with 1:08 left in helping Buffalo overcome a 14-point deficit.
Lewis also scored on a 3-yard run and lost a fumble. In playing through the injury for most of the game, Lewis wasn't sure when he was injured.
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