The Buffalo Bills defense ranked among the best NFL defenses last season. The Bills allowed the second-fewest amount of yards to opponents and led the league in opponent passing yards per game. The Bills also held teams to the least plays per drive and least yards per drive.

Still, head coach Sean McDermott needs the Bills to be better.

"All of it. We have to be better defensively. Last year's defense was last year's defense. This year's defense is a new defense made up by different guys even though there has been a lot of continuity to your point. I say this respectfully, we've got work to do on that side of the ball also," McDermott said.

Now the Bills will have to find a way to maintain the same success with almost the same roster as last season. Here are five ways the Bills defense made progress this offseason:

1. Tremaine Edmunds growing as a leader

Edmunds first year in the NFL went by in a flash and by December of his rookie season he began to earn accolades for his effort on the field. Edmunds was named the Defensive Rookie of the Month for December and recorded 43 tackles, two interceptions and four passes defensed in five games.

As the game slows down for him, there's a bright future for the 2018 first-round pick.

"Probably the biggest thing is the confidence. It's extremely high now and you see it in the way he communicates, he has a much better grasp of what we want to get done on defense and what his role is within that," said defensive coordinator Leslie Frazier.

Edmunds has received help from veterans like Lorenzo Alexander and Kyle Williams.

"I'm trying to leave a legacy for the future Buffalo Bills and a big part of that is how much of a leader Tremaine becomes," Alexander said. "So I'm trying to help that process along as fast as possible."

Throughout OTAs and minicamp, Frazier saw Edmunds as that future leader.

"His ability now to communicate with no hesitation, to know exactly what we're looking for as a coaching staff, you see the evidence in the way he's practicing and the way he's communicating with his teammates, which gives those guys confidence in our middle linebacker," Frazier said.

2. Finding Kyle Williams replacement

The Bills were thrilled when they landed defensive tackle Ed Oliver at No. 9 in the 2019 NFL Draft, but he hasn't earned the starting spot yet, for now that belongs to Jordan Phillips.

Phillips signed a one-year deal with the Bills in March and will now compete with Oliver for the starting three-technique position. Since signing his deal, Phillips has been determined to earn the starting role and prove he's can be a top defensive tackle.

"Buffalo gave me an opportunity and I felt that they should reap the benefits of the success that I'm going to have," Phillips said.

Oliver is no slouch on the second team. The Bills are confident he can contribute as they watched him play throughout the offseason

"Ed's done a really good job up to this point," Frazier said. "I don't think it's been overwhelming for him, with the meetings along with what we're doing on the practice field. You see his quickness, you see his burst. As he continues to get a better grasp on what we're asking him to do on defense, I think you'll see more of his athleticism as well. Up to this point, we've been impressed with what we've seen and we'll just keep watching his maturation over the next few months."

3. Deeper group in the secondary

With Tre'Davious White, Micah Hyde, Jordan Poyer, Levi Wallace already leading the charge for the Bills secondary, Buffalo focused its defensive free agent acquisition effort by adding depth for this group. The Bills brought back E.J. Gaines and added former first-round pick Kevin Johnson to add more competition at the cornerback position.

White, Poyer and Hyde are locks for their starting spots but the competition heats up at the No. 2 cornerback spot and the nickel. Johnson was named a standout for the Bills by ESPN this offseason and second-year corner Siran Neal has been making his presence known as he converts to the nickel spot.

"You saw the ability coming out of college," Frazier said on Johnson. "He did a really good job in his rookie year, off to a really good start. The injuries have kind of creeped up. We're hoping that he can stay healthy, we know he has the talent to really help us."

Wallace still holds his starting spot from last year and earned the highest Pro Football Focus grade of any first-year cornerback, along with the highest coverage grade.

4. Keeping personnel the same

The Bills have stressed continuity and building a familiarity between teammates. It's been tough on the offense with multiple players missing time due to injury but the defense has stayed injury-free throughout OTAs and minicamp.

The Bills first-team defense has stayed relatively the same as last season and the ability to come in and work with the same group has been beneficial for Hyde.

"It's huge for communication purposes," Hyde said. "I know where Poyer is going to be at all times, I know where Tre'Davious, Tremaine, the D-line, same thing. I know what they're going to be in so once you can pinpoint where everybody's going to be and you know your job, the sky's the limit."

Specifically, it's helped Hyde and Poyer. The two safeties describe their play sometimes as "freelance" and are able to give Josh Allen different looks and figure out what works.

"We have a good understanding of what we are doing on the football field," Hyde said. "We're always talking and communicating and that goes for whoever is on the back end. As long as we keep communicating and keep talking we can be a great defense."

5. New mindset

Be more physical and be nastier has been McDermott's emphasis to the defense this offseason. McDermott was unimpressed with the physicality of the defense last year and wants it upped for 2019. The main goal that comes with a more physical and nastier defense? More takeaways.

"I'm seeing just a lot of guys flying around, a lot of guys making plays on the ball," linebacker Matt Milano said. "That's been the emphasis is just getting takeaways and making sure everybody's running to the ball because you never know what can happen. Somebody strips it out, whatever it may be, but just good things happen when you do that."

"Knowing the situation and obviously anticipating is really what it comes down to. If you know the situation that you are in, you can anticipate not only what you are going to do but what the opponent is going to do. That gives you a chance to be a step ahead or half a step ahead and, in this case, and that's where turnovers happen," McDermott said. "When we can put people behind the sticks and put us in favorable positions where it's third and long, fourth and long, or second and long, usually when you can do that that's putting pressure on the offense on the opponent and that's where turnovers tend to happen."