ORCHARD PARK, N.Y. — It wasn’t a good sign for the Bills’ defense this week when cornerback Ron Brooks was put on injured reserve and virtual unknowns Sammy Seamster and Bud Noel were promoted to the active roster five days before taking on the resurgent Ryan Fitzpatrick and the Jets.

Seamster and Noel, both undrafted, have appeared in two NFL games combined. The thought of them being forced into action Sunday was surely an uneasy one for coach Rex Ryan as he prepared to play his former team.

But good news came Friday on that front: cornerback Ronald Darby, a defensive rookie of the year candidate, will play Sunday after missing last week’s game with a groin injury.

“Thank goodness,” Ryan said. “He was doing whatever he could to get here and it looks like he’ll be a go.

“They do a ton of four-wides to begin with, and, you know, having our situation, having Darby is big. It got a lot better for us having him back.”

Darby’s return should give Ryan’s defensive backfield some degree of stability as it looks to slow Fitzpatrick, the Bills former quarterback who’s enjoyed a career year with the Jets and can set the franchise record for touchdown passes in a season Sunday.

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Behind Darby is Leodis McKelvin, who has also played some safety this year; Mario Butler, who made his first career start last week; Nickell Robey, who played a season-low 24 snaps last week; and then Seamster and Noel.

They’ll be tasked with shutting down receivers Brandon Marshall and Eric Decker, who have at least one touchdown each in eight games this season — a record for a wide receiver duo.

“We’ll see what happens,” Ryan said. “If we have to play a few more safeties or whatever then we can do that as well. But we’ll make it work.”