If there's one thing to take away from the Premier League season, it's that you won't get very far up the table if you can't set your team up to defend.
You only have to look at the goals conceded columns for the current top three.
Chelsea: 4. Manchester City: 6. Liverpool: 11.
And that's having played 12 games, including some against each other.
Compare that with the mess at Manchester United - with Ole Gunnar Solskjaer presiding over 21 goals conceded from the same number of matches - and it shows how a watertight defence is the new barometer for a title contender.
It's not something that you would commonly associate with Pep Guardiola, Jurgen Klopp or Thomas Tuchel - coaches of those respective three sides.
But it's been a theme for a few seasons now, with Manchester City's title-winning side of last term a study in parsimony, keeping a remarkable 19 clean sheets.
Of course, these three coaches achieve a tight defence in different ways.
Guardiola, Klopp and Tuchel's methods
City hog the ball to such a degree that opposing teams have to do something with so few chances and touches of the ball, and Guardiola is also obsessive about shape to guard against counter-attacks.
Klopp is renowned for violent counter-pressing, thus keeping the ball away from his own goal as much as possible, whilst also having high-quality, pacey defensive individuals when teams do break the trap.
Tuchel - whose team already have a remarkable 12 clean sheets in all competitions this campaign - plays 3-5-2 and drills his players to know their roles so clearly that breaking them down only happens on rare occasions, at which point it helps having one of the best 'keepers in the league behind them in Edouard Mendy.
Manchester United by contrast have exhibited none of the control that the aforementioned three sides have.
They attack and defend as individuals, and as such when they lose the ball they are often in no sort of structure to try and protect against an opponent's transition - as seen on multiple occasions this season, not least the home thrashing by Liverpool.
There is a common theme here, in that all three of Guardiola, Tuchel and Klopp managed in Germany, with the latter two cutting their managerial teeth at Mainz and Borussia Dortmund.
And there is another man on the same path behind them.
Bo Svensson is the current coach of Mainz, who have conceded fewer goals than Bayern Munich in the Bundesliga this term and who kept five clean sheets in their first six league games.
Unsurprisingly perhaps, Svensson spent time under both Klopp and Tuchel as a player at Mainz.
"Of course, I benefitted from their expertise and working patterns," Svensson said when becoming Mainz coach in January 2021.
"Their way to deal with people and lead a team stayed with me, as well as their game approach. All aspects influenced me next to the growing desire to become a coach.
"It would be crazy not to adopt things that made them some of football's greatest coaches."
The fact Svensson has got his team playing this way despite taking over last season when they were bottom with just six points shows what an impact he has had.
"We have known for a while there is a new great coaching talent around," Mainz board member Christian Heidel said of Svensson last season after Mainz had beaten Bayern Munich.
And it may not be long until we see him follow his idols to the Premier League.