The great Eagles defense of 1991 received some attention this past week. Football Outsiders wrote a piece on the greatest defenses of the past 30 seasons and ranked Gang Green as the best of the best. The Eagles finished first against the run, the pass, and in total defense. Gang Green is the only defense to pull off that feat in more than 40 years. That was a truly special unit.

The Eagles finished 13th in yards allowed last year. They were 13th against the run and 15th against the pass. There were times when the defense looked great. They only allowed nine points per game in the first three weeks. No team gained more than 288 yards on them in the first month. There was the game against the Vikings when the defense had six sacks and came up with four takeaways. The Eagles played the powerhouse Falcons and held them to 48 rushing yards and 15 points, their lowest totals of the season. To put that in perspective, Atlanta scored 43 points the previous week and rebounded with 38 the following game. Holding them to just 15 points was truly impressive.

There were lows as well. It was torturous to watch the Eagles surrender 230 rushing yards to Washington in a home game. Giants quarterback Eli Manning threw for 356 yards in a late-season meeting. The Bengals scored 32 points in what was probably the low point of the season. Interestingly, the Bengals were the only team to score more than 30 points on the Eagles all year long.

Overall, Jim Schwartz's defense played well. But that's not good enough for Schwartz or the Eagles. They know the defense has to be better. The Eagles have been to a pair of Super Bowls. The 1980 team was No. 1 in scoring defense and third in yards allowed. The 2004 team was fourth in scoring defense and ninth in yards allowed. When this franchise wins big, it plays great defense.

That raises the question of how good can the current defense be?

I think this group has tremendous potential. The key to success under Schwartz is having a defensive line that can dominate. The line was good last year, but inconsistent. The Eagles let Bennie Logan leave in free agency but replaced him with Tim Jernigan and Elijah Qualls, a pair of talented interior pass rushers. The Eagles released Connor Barwin, replacing him with Derek Barnett and Chris Long, a pair of talented edge rushers. The line is deeper and more talented than last year.

The 2016 line racked up 28 sacks and eight forced fumbles. Those numbers should go up this season. Fletcher Cox and Brandon Graham were very good last year, but it was their first season working with new coaches and playing in a new scheme. They will know their roles and the scheme better this year and should be more productive. Vinny Curry was hampered by nagging injuries last year. If he can stay healthy, Curry can take a big step forward.

The additions of Jernigan and Long can help quite a bit. Jernigan is a terrific interior rusher. He had five sacks last year in Baltimore. Long had four sacks, rushing both off the edge and up the middle for the Patriots. That gives Schwartz two veteran players who can step in and contribute right away.

What about the rookies, Barnett and Qualls? Rookies have produced for Schwartz over the years. Ziggy Ansah had eight sacks as a rookie in 2013. Ndamukong Suh had 10 sacks in 2010. Jason Jones had five sacks as a situational rusher in 2008. Late-round pick Jacob Ford had seven sacks as a situational rusher in 2007. Defensive tackle Randy Starks had 4.5 sacks as a part-time starter back in 2004. Seventh-round pick Carlos Hall had seven sacks off the bench in 2002. That's a variety of players with different sizes, skill sets, and talent levels who all had success for Schwartz as rookies.

Barnett and Qualls are athletic pass rushers who can contribute this season. Barnett could be a real X-factor. He could be an excellent backup but also has the potential to push for a starting role this year. Barnett was highly productive at Tennessee. He knows how to get to the quarterback. Barnett stood out in the Organized Team Activities and minicamp. He does not look like your typical rookie. Barnett looks like a player who is going to force the coaches to put him on the field.

If the defensive linemen can stay healthy and play to their potential, the Eagles could have one of the best defensive lines in the NFL. This is a deep, talented, and versatile group. Schwartz can be creative with how he uses them. Cox can line up at end with Curry on the inside. Jernigan can play any spot. Long and Graham have played inside in the nickel defense in their careers. It will be fun to see how the coaches use their weapons. There could be some really interesting combinations this season.

Nigel Bradham and Jordan Hicks looked like Pro Bowl linebackers at times in 2016. The challenge for them is to play at that level all year long. Hicks is a major playmaker in coverage. He picked off five passes and was credited with 11 passes defensed, very high figures for a linebacker. Hicks can still improve against the run. The middle linebacker should be a tackling machine, flying from sideline to sideline. Hicks finished fourth on the Eagles in total tackles, his first season playing middle linebacker in the NFL. He needs to be more active and productive against the run this year. Bradham needs to be more disciplined. There were times when his desire to make plays got him out of position and hurt the defense. Mychal Kendricks will play in the base defense and some specialty packages.

This is the most talented trio of 4-3 linebackers the Eagles have had in a long time. Hicks could develop into a star player. All three linebackers can defend the run, blitz, and cover. If the defensive line is as disruptive as expected, there should be plenty of chances for the linebackers to make plays. Schwartz and his staff have a good idea of what the players can do now so it will be interesting to see how he uses them this season. 2016 was a learning experience for the coaches as well as the players.

While the Eagles' front seven should be among the best in the league, things are less certain on the back end of the defense. The team has a terrific pair of safeties in Malcolm Jenkins and Rodney McLeod. Cornerback remains wide open. The Eagles hope veteran Patrick Robinson plays well and can be a reliable starter. Rookie Rasul Douglas and second-year corner Jalen Mills are also in the mix to start. Robinson and Mills could also play the nickel position. Or that could go to Aaron Grymes or Ron Brooks. The Eagles need some players to step up and win roles.

The Eagles' long-term outlook will depend on the health of Sidney Jones. He has the potential to be an outstanding cover corner. The Eagles must have one cornerback become an above-average player for this defense to become an outstanding unit. The team will bring Jones along slowly because they know how important he is to the future of the team.

It takes time to build a great defense. Go back to Gang Green. Buddy Ryan inherited Reggie White, Wes Hopkins, and Andre Waters. Ryan drafted Seth Joyner and Clyde Simmons in 1986. Jerome Brown and Byron Evans were drafted in 1987. Eric Allen was picked in 1988. Corner Ben Smith was added in 1990. William Thomas came along in 1991. That group became great over time. Part of that was due to simply adding more talent. They also mastered the scheme. Ryan ran a complex defense that took time to grow into. It also takes time for a group of players to develop chemistry and to become close as a unit.

The 2017 Eagles won't be a finished product. Schwartz has talented pieces to work with. He has playmakers at each level of the defense. Time is still needed for this group of players to master the scheme and to continue to grow together. There is always a need for more talent.

I do think this group has the potential to be a top-five defense. The front seven has the potential to be dominant. The secondary has playmaking safeties. That is one heck of a start. Cornerback is the big question mark. The key is that there are some young guys with potential. That hasn't been the case in recent years.

Could this defense become something special? That is possible but would require two or three Eagles outside of Cox to become great players. You need Hall of Fame-type performances for a unit to be special. Even Cox, the team's best defensive player, would need to take his game up a notch.

For now, the Eagles need to focus on being better than last year. That means making more plays and giving up fewer points. The talent is there. The potential is there. It is up to the players to get the job done and get this team back in the postseason.

Tommy Lawlor, goeagles99 on the Discussion Boards, is an amateur football scout and devoted Eagles fan. He is the Editor of IgglesBlitz.com.