They stand, side by side, lauded by many as the two greatest single-season defenses in NFL history: the 1985 Chicago Bears and the 2000 Ravens.
The comparisons constantly come up, especially with the recent 15-year anniversary of that dominant Ravens squad and the 30th anniversary of the Bears' defensive unit.
The arguments will long rage as to which was better, but one irony has become clear as time has progressed: one keeps helping the other.
With the appointment of ex-Bears cornerback Leslie Frazier to the Ravens' coaching staff Jan. 15 as their new secondary coach, Baltimore has tapped into the 1985 Bears reservoir for the third time:
- Rex Ryan, whose father, Buddy, was the Bears' defensive coordinator, helmed the Ravens' 2000 defensive line and later became their defensive coordinator.
- Chicago middle linebacker Mike Singletary coached the Ravens' inside linebackers -- including soon-to-be fellow Hall of Famer Ray Lewis -- during Baltimore's 2003-04 seasons, the former of which ended in the Ravens' first of four AFC North Division titles.
- The 56-year-old Frazier was a starting corner on that memorable Bears team and led Chicago with six of his 20 career interceptions. It turned out to be the last of the five squads on which he would play, as his career would end due to a knee injury he incurred while running back a punt during his team's 46-10 Super Bowl XX rout of the New England Patriots.
That game took place in the now Mercedes-Benz Superdome, site of the Ravens' second Super Bowl triumph, which would come 27 years later. Coincidentally, it would take approximately that long before he appeared on the Ravens' radar.
Having paid his dues the way coaches usually do -- via the small- and major-college route -- Frazier put his experience to work for five different NFL teams before becoming the 12th Ravens assistant to have any sort of affiliation with the secondary, most of any position unit in franchise history.
Even in football's alpha-male world, Frazier brings a calm demeanor and attention to detail to his new position, something for which his ex-head coach, 1985 Bears leader Mike Ditka, could vouch two years ago when Frazier was named the Tampa Bay Buccaneers' defensive coordinator.
"I played for Coach [George] Halas and I played for [Tom] Landry, two complete opposites in the sense of personalities," Ditka told the Tampa Bay Times. "And Leslie had a Tom Landry personality, he had the knowledge, he had the understanding of what it took to get the best out of people and he did it in a very quiet way. And I think that's good.
"Some people do it different. [Vince] Lombardi did it different. I did it different. But you have to be who you are, and he stayed true to who he is."
If the Ravens' defensive backfield can show the same kind of improvement that others have under Frazier, it will prove to be an astute hire.
Frazier got to coach multiple Pro Bowl players Troy Vincent and Brian Dawkins during a four-season run in Philadelphia from 1999-2002. While in Cincinnati in 2004, Frazier was the defensive coordinator for a Bengals squad that recorded 20 interceptions, the most in eight years, and 36 total takeaways, the league's third most that year.
Two years later, when Frazier was Indianapolis' secondary coach, the Colts went from 15th in pass defense the previous year to the league's second best, helping to key a run that ended in a Super Bowl XLI win against the Bears.
A head coaching stint in Minnesota from 2010-13 didn't work out so well, but Frazier rebounded as the Buccaneers' defensive coordinator the past two years to field the league's 10th-best overall defense in his second season (2015).
Frazier -- having worked with Ravens head coach John Harbaugh during one of his stints in Philadelphia -- lends valuable all-around coaching experience to the Ravens' staff as the ninth former head coach to work under Harbaugh in Baltimore, the third on the current staff following quarterbacks coach Marty Mornhinweg (Detroit) and offensive coordinator Marc Trestman (Chicago).
With veteran coaches and younger players around him, Frazier will have an assortment of people with whom he must work to make the Ravens better as quickly as the fans expect.
"Leslie is a good teacher, communicator and encourager," NBC analyst Tony Dungy told the Tampa Bay Times. "Again, he knows how to win. He's been a player in the Super Bowl and knows what it looks like. He went on to Philadelphia with Andy Reid, he won the Super Bowl with us in Indianapolis.
"It's not just credibility, you know what it takes. It's the discipline and details. They'll get it from the head coach and defensive coordinator and the coaching staff and it filters down."
Just as Frazier was a 1981 Bears signee -- catching the team in its ascendancy into one of the league's best -- he could be latching on to the Ravens' cover men at exactly the right time.
Despite spotty play the last two seasons, the Baltimore defensive backs generally avoided the team-wide injury bug that plagued the squad in 2015.
Cornerback Jimmy Smith played through a lingering foot injury during the season's first half and went on to start all 16 games, one of only seven Ravens who could make that claim. Fellow corner Lardarius Webb started 15 games as he began his gradual transition back to free safety.
Speaking of safeties, starting duo Kendrick Lewis and Will Hill were partnered in nearly every game, with only Lewis missing one contest.
Frazier knows he will have an experienced starting quartet coming back next year, as all four principal starters are under contract for 2016. But another key point is that most of the main reserves are also returning, with the possible exception of cornerback Shareece Wright, who will be an unrestricted free agent when the new league year begins March 9.
Wright rounded nicely into form last season after being hastily thrown into the lineup against his former San Francisco teammates during Week Six and allowing a long touchdown catch by former Ravens receiver Torrey Smith.
But after a series of embarrassing performances like that, the secondary pulled itself together and was one of the league's best coverage units during the season's second half.
Despite a franchise record-low five interceptions -- the team's only other pickoff came from linebacker Daryl Smith -- the Ravens' defense allowed more than 200 passing yards in just two of the season's final eight games after yielding more than that number during six of the first eight contests.
Defensive coordinator Dean Pees has often cited that ill-timed coverage breakdowns and the resultant big plays -- defined as pass plays that gain more than 20 yards -- were the biggest reason for the team's slow start, one that translated to a 1-6 record and an early start toward the following year.
Indeed, many thought that it was the secondary's breakdown that would lead to Pees' dismissal, but Frazier's hiring and the move of 2015 secondary coach Chris Hewitt to an assistant's role under him could lead to an overall bolstering of the coaching staff.
What could also help is the drafting and free-agent signings of even more secondary players who could fit into the kind of Cover-2 system Frazier ran in Tampa Bay. That system gives safeties wider sideline-to-sideline responsibilities in the defense's back end and often involves corners handing receivers off to them as they get deeper.
Frazier has been known to tinker with, if not totally depart from, the Cover-2. With passing attacks getting more sophisticated every year, change might become a necessity. But for Baltimore fans, so is winning.
Yet another member of the 1985 Bears might help the Ravens do just that.
Joe Platania has been covering professional football since 1994.