Tyrod Taylor has established himself as the clear No. 1 quarterback for the Buffalo Bills, leaving EJ Manuel as his backup.

Manuel, who was a first round pick in 2013, will be unrestricted free agent after this season.

"My focus right now is just finishing whatever I have here," Manuel said. "Whatever my situation is, wherever I'm at, I have to put myself in the best position moving forward, but also help this team win. That's the most important thing."

The only way Manuel will get a significant amount of meaningful snaps is if Taylor goes down with an injury.

"The team feels great about him," Rex Ryan said. "I love his preparation. It's never wavered. In fact, I think he's better now than I've ever seen him. So, you know, I'm really happy with EJ."

Marcell Dareus announced Saturday that he is entering a rehabilitation facility.

The NFL announced Tuesday that Dareus will be suspended for the first four games of the regular season for a violation of the league's substance-abuse policy. Dareus told reporters Wednesday that he missed a drug test.

"After careful consideration of recent events within my life, I have made the decision to enter a rehabilitation facility," Dareus said in a statement released Saturday by the team. "I feel this is the best decision for me, my family and my teammates as I move forward with my career. I appreciate the support of my teammates and the Bills organization through this process."

"We are fully supportive of Marcell and this decision to take the time he needs to seek treatment," the Bills added in a separate statement.

Karlos Williams has been waived by the Buffalo Bills.

The NFL announced in July that Williams is suspended for the first four games of the regular season for a violation of the league's substance-abuse policy. He can serve the suspension as a free agent if he is not claimed off waivers or signed by another team.

Williams reported to minicamp in June out of shape.

A fifth-round pick last season, Williams played in 11 games, starting three. He gained 517 yards on 93 carries and scored seven rushing touchdowns in addition to two receiving touchdowns.

The Buffalo Bills defense will be better in 2016 despite key injuries to rookies Shaq Lawson and Reggie Ragland, as well as the four-game suspension of Marcell Dareus, according to Rex Ryan.

"I see the big picture. I also see this defense is improving," Ryan said. "I've said it from Day 1: we're going to be better. We will definitely be better than we were last year, in my opinion. Regardless of those [injuries and suspension], this defense will be better."

In Ryan's first year as coach, the Bills finished 19th in yards allowed last season. They had the NFL's fourth-ranked defense in 2014 and Ryan predicted upon taking the job that his unit would be the NFL's best in 2015.

Marcell Dareus is facing a four-game suspension for another violation of the NFL's substance abuse policy.

Dareus was suspended one game last year for a violation of the league's substance abuse policy.

The Bills already are without rookie pass rusher Shaq Lawson, who is expected to miss at least the first month of the season after undergoing shoulder surgery, and rookie linebacker Reggie Ragland, who had season-ending knee surgery last week. Bills linebacker IK Enemkpali also will miss the season because of a knee injury.

The Buffalo Bills have agreed to a long-term contract extension with Tyrod Taylor, according to multiple reports.

The extension is worth $92 million over six seasons.

Taylor had been set to enter the season with a contract with an average annual value of $1.1 million, the lowest among the NFL's starting quarterbacks.

"Every year you have something to prove," Taylor told reporters Friday. "This is a competition-driven league. It's not like the NBA where everything is guaranteed. You can get cut at any given time. Any time you step on that field, you have something to prove, and that's been my mindset every time I step on the practice field."

Reggie Ragland will undergo surgery for a torn ACL in his left knee and is expected to miss the entire 2016 season for the Buffalo Bills.

The Bills were already without first round pick Shaq Lawson and now they'll be without their second round pick in Ragland.

Ragland suffered the injury in practice last Friday while pursuing running back Reggie Bush on a play during 11-on-11 drills.

Doug Whaley said after the draft that Lawson, Ragland and third-round pick Adolphus Washington were all expected to start immediately for Buffalo's defense.

When the Buffalo Bills signed Reggie Bush he looked like an insurance policy, but Rex Ryan may have bigger plans for the veteran running back.

"First off, with Reggie Bush, he's such a talent but we want him to be almost like that Ferrari that we unleash and let people be like "Oh man, he's out there!" But I also don't want to run him into the ground," Ryan said.

Bush signed a one-year, incentive-laden deal with Buffalo.

Reggie Bush has signed a one-year deal with the Buffalo Bills. Bush spent the 2015 season with the 49ers.

The Bills will be without Karlos Williams for the first four games of the 2016 season.

Bush tore the meniscus in his left knee slipping and falling on an exposed concrete surface surrounding the field in the Edward Jones Dome in St. Louis.