ORCHARD PARK, N.Y. -- Rex Ryan might have won over his Buffalo Bills players with his easy-going style, but in opening competitions at several starting spots this week, Ryan has sent a message to the locker room of his reeling, 4-5 team: he's not their friend.

"I'm tired of mistakes and I think we've got to get better physically as well," Ryan said Wednesday. "And if that's through technique and all that, that's what it's going to be. I'm not here to make friends, man. I'm here to win."

Having returned from their bye week, the Bills travel to play the Cincinnati Bengals this Sunday with their playoff chances resting on thin ice. FiveThirtyEight.com's metrics peg the Bills' postseason chances at 20 percent, while Football Outsiders' latest projection gives the Bills a 13-percent shot at earning a playoff berth. Buffalo sits in 11th place in the AFC standings and has a 1-4 conference record that could prove unfavorable in wild-card tiebreakers at the end of the regular season.

"We can't back up anymore," Ryan said. "We can't afford to slip up. We understand that."

Upset with some players' performances over the Bills' current three-game losing streak, Ryan has publicly put several players on notice while he shakes up repetitions with the starting group in practice. Right tackle Jordan Mills is in danger of losing his job to Cyrus Kouandjio or Seantrel Henderson, once-promising starting cornerback Ronald Darby has split reps with veteran backup Corey White in practice this week and nickel cornerback Nickell Robey-Coleman said Wednesday that rookie Kevon Seymour has all but taken over his job.

"I ain't really get no reps today," Robey-Coleman said. "Everything was all Kevon. I think it's pretty much gonna be all Kevon from here. That's where it's at right now. It's gonna be all Kevon Seymour."

Robey-Coleman, an undersized slot cornerback who earned the respect of coaches and teammates when he made the Bills' 53-man roster as an undrafted free agent in 2013, has been a constant presence in Buffalo's defense since his rookie season. Among his notable miscues in recent weeks have included being closest in coverage on a 53-yard touchdown by Rob Gronkowski in an Oct. 30 loss to the Patriots, and trailing Jimmy Graham on an 18-yard touchdown in the Nov. 7 loss to Seattle.

Noting Wednesday that is was "tough" guarding two of the game's best tight ends, Robey-Coleman responded professionally to being benched, saying, "Is this what I want? No. But if this is where the team is got to get better, then that's what we're gonna do. I'll take that on the chin. Whatever to make the team better and to make the team win, I'm all for."

The midseason competition for starting jobs has sent a message to the Bills' locker room, which has been used to Ryan's well-known loose and positive style. Until now, Ryan's approach has often resulted in the coach publicly defending his players -- not benching them.

"We all know that our jobs are on the line, essentially," linebacker Preston Brown said Wednesday. "We gotta win games, no matter whether we're friends [with Ryan] or not. ... If Rex gotta be more tough and get guys on edge and make them play harder, if it works, it works. So we're all on board with it."

However, players did not go as far as to say Ryan has changed as a coach. Cornerback Stephon Gilmore attributed the shift in tone from Ryan to the losing streak, and Robey-Coleman believes the "fun stuff" from Ryan will return once the Bills begin winning again.

"We know it's still Rex," Brown said. "He's still going to be friendly as much as he wants to say [he won't]. He's still a great guy. It's definitely still fun being around him. But we know the mentality is gotta change now if we don't get these wins."