ASHBURN, Va. -- The optimism stemmed from a defensive front considered one of the best in the NFL. It fueled the Washington Football Team's belief it could, once again, have an elite defense after ranking No. 2 in the NFL last season. And, without a top quarterback, that defense would be needed.

Through two games, however, the defense's play has produced more questions than optimism after allowing 49 points and 815 yards. The biggest question: What has gone wrong? Washington needs an answer before Sunday when it faces quarterback Josh Allen and the Buffalo Bills (1 p.m. ET, Fox).

And the schedule doesn't get any softer, with a gauntlet of quarterbacks highlighted by matchups against Patrick Mahomes (Kansas City Chiefs), Aaron Rodgers (Green Bay Packers) and Tom Brady (Tampa Bay Buccaneers) during a four-game stretch that begins in Week 6.

"I expect us to be better," Washington coach Ron Rivera said.

The talent hasn't changed, so the defense could turn it around. Washington still has Chase Young and Montez Sweat at end and a deep rotation at tackle.

"There's no reason for it to change," Rivera said of high expectations.

What must change are the results. The defense enters Week 3 ranked No. 25 in yards, No. 17 in points allowed and No. 30 on third-down conversions. Last season, the unit ranked No. 2, No. 4 and No. 6, respectively, in those categories.

"We just have to do better," defensive tackle Jonathan Allen said after beating the Giants, 30-29 in Week 2. "It's not like the issues are we're just not good enough. We obviously have the talent. We just got to focus on the little things, and honestly, thank God our offense was there to save us time and time again."

Backup quarterback Taylor Heinicke, thrust into the lineup when starter Ryan Fitzpatrick suffered a hip injury in Week 1, has been a feel-good story and led two late scoring drives against the Giants. But it's unclear when Fitzpatrick might return and relying on the offense is not the winning recipe for a team built with the defense as its backbone.

Rivera has pointed to undisciplined play as a culprit in Washington's early defensive struggles. It's not just the same player or unit that makes the mistakes. Sometimes it's a linebacker not fitting in the right gap, leading to Giants running back Saquon Barkley ripping off a 41-yard run. On a pivotal third-and-16 against the Los Angeles Chargers late in a 20-16 opening-game loss, there were two coverage gaffes -- linebacker Jon Bostic was way too wide and the safety didn't get to the middle of the field -- leading to a wide-open completion over the middle.

"You get an opportunity to make a play, make it, but don't try and create it," Rivera said after the Week 1 loss. "Because if you do, that's what's going to happen. You're going to make mistakes."

Rivera doesn't want to be patient, knowing why the issues arise.

"I expect it to be fixed now," he said. "It was more of a matter of being disciplined. This defense, the way it's designed, it's about accountability. You have a gap assignment. You have a coverage assignment, you have to do it."

Sometimes the linemen lose their gaps, leading to issues. There were poor angles taken against Giants' quarterback Daniel Jones (95 rushing yards) on zone-read keepers, whether it was a lineman (James Smith-Williams) or a safety (Landon Collins). Collins has had some issues in coverage the first two games as well.

There's a rookie linebacker, Jamin Davis, who is still learning. At times, for example, he has reacted to motion by the offense based on his assignments at Kentucky -- which is more than what he's supposed to do with Washington. Against the Chargers, when that happened it led to bigger gaps for the running backs.

"The first play of the game I got put on my butt," Davis said of the opener. "My alignment was wrong. [I learned] to simply just be where I'm supposed to be with my alignment before the play starts. ... I feel like I'm there now and it's just me playing with my hair on fire."

He was more active in Week 2, which is why Rivera was pleased with his showing, but he's still a work in progress.

"You saw some of his quickness and speed in some of the coverage things as well," Rivera said.

The four-man pass rush also has not been as effective as hoped. Washington has three sacks from a four-man rush over two games. Part of the problem is that opponents have used more play-action in the first two games, successfully slowing the rush. Last season, teams passed the ball 7.4 times per game using play-action; in two games this season it's 10 per game. The Giants also chipped or doubled-teamed Sweat and Young at least six times apiece.

"I feel like you just got to stay active and you just got to keep going hard," said Young, who has four tackles and no sacks in two games.

Finally, only one team -- Tampa Bay -- has faced more protections of six blockers or more than Washington's 39, which is two fewer than the Buccaneers.

That's why Washington has used more five-man, or more, rushes. Last season it used that strategy 11.9 times per game; in two weeks this season it has used it a combined 40 times, according to ESPN Stats & Information.

Washington's youth could be a factor. It has 12 defensive players -- starters or key reserves -- who are 26 years old or younger, and seven who are 24 or younger. Young, Davis and cornerback Benjamin St-Juste are 22. That youth has led to excitement for the future, but also some growing pains.

"It's about performance, not about potential," defensive coordinator Jack Del Rio said before the season. "There are a lot of teams with potential that don't do a whole lot."

Rivera said he's shown his defensive players many examples of what happens when they all fit in the right gaps. The players see the positive results, hammering home his point.

"It's all fixable," Rivera said. "If it wasn't fixable, if we weren't good enough I wouldn't be as frustrated as I get at times. This is a good team. When you bring back as many guys as we have you should be getting ready to take another step, and that's what I expect to see from us going forward."