For all that attention may be focused on events at Old Trafford this Sunday, both Millwall and Blackburn have done more than most to inject real energy and life in the old competition over the last few years.
In 2004, just as the 'big four' started to take hold of the top end of the Premier League, Millwall became one of the last Championship sides - other than Cardiff in 2008 - to reach the FA Cup final. In the last round of FA Cup fixtures this season, then, Blackburn Rovers actually knocked out one of that traditional four, and just at a point when Arsenal desperately needed to win.
As such, it's perhaps appropriate that it's the FA Cup itself effectively keeping these two teams' seasons alive. Because, right now, they're destined for the dredgery of the Championship mid-table.
Blackburn haven't actually picked up a single point since their defeat of Arsenal, just over a month ago, and have seemingly lost the impetus recently-installed manager Michael Appleton initially gave them, while Millwall have remarkably lost seven of their last eight.
The only win for the latter, in fact, was a 2-1 victory away to Middlesbrough. Otherwise, Millwall have lost all four of their last league games at home. A 2-0 defeat to Wolves on Tuesday marked a particular nadir, with manager Kenny Jackett talking on Friday of making changes - not just in terms of personnel, but also attitude.
"We have talked about Tuesday," he said. "It is a thin dividing line between giving an honest assessment and destroying confidence. As managers, we have to tread that tightrope but we have got a real honest bunch and we want to come out positively.
"I do not see too many divisions or problems with the guys. There is a good attitude in terms of coming into work and training. That is not an issue and not a problem."
Appleton, meanwhile, struck a similar chord.
"I think this is an opportunity to put the league to bed for a few days," he said. "We've got a great opportunity to go and play at Wembley, it has been a while since the football club did that. So I'm sure the players will grasp that, they've got an opportunity to do something special."
In general, though, Blackburn have the joint worst away record in the league so, either way, something is going to give this weekend.
More than anything, though, this is a match between two teams effectively fighting for their seasons: and that should make it a hugely compelling - and properly do-or-die - cup tie.
Millwall player to watch - Adam Smith
Millwall may have fallen back in the league of late, but the 21-year-old right-back is only making massive strides while on loan there. He'll provide plenty of energy to this encounter.
Blackburn Rovers player to watch - Jordan Rhodes
The livewire striker has provided value for his £7m price tag, scoring 20 goals in 36 appearances this season. The one thing missing from his CV so far, though, is a goal against a Premier League club. Hit a decisive strike on Sunday, and he will very likely get another chance.
Trivia: this is the first time in the history of the FA Cup that both Millwall and Blackburn have been in the sixth round at the same time. This is also the first quarter-final not to feature a Premier League side since 2008.
Stats: Blackburn have claimed victory in the two previous times these sides have met in the FA Cup. They are also one of only two sides, along with Manchester City, not to concede a goal in the FA Cup this season.
Odds: Millwall (1.4), Blackburn Rovers (1.9) and the draw (2.3) are available at Bet365. Rhodes is 4.0 to be first scorer.
Prediction: Millwall to build on their FA Cup form, and just shade it.