Defense wins Champions Leagues. A cliché it may be, but in this competition in particular the kernel of truth has grown into an uncrackable nut. Manchester City, Chelsea, Bayern Munich: all have lifted Europe's greatest prize because in the moments that matter most, their backline has held firm. The last four Champions League finals have all finished 1-0.

If Borussia Dortmund are hoisting the European Cup on Saturday night you can rest assured that they will be placed into that lineage. Mats Hummels will be player of the tournament, Gregor Kobel will be the hottest  goalkeeper on the transfer market again and everyone will be asking why Chelsea have spent so much money on left backs when they have had Ian Maatsen on their books.

In a way, all that praise would be merited. Kobel has kept six clean sheets this season, two more than any other player in the competition. The team record of nine goals conceded in 12 games is the joint best per match defensive record in the Champions League, level with Real Sociedad. All that has been accrued against a murderer's row of opponents, the group of death followed by freewheeling PSV Eindhoven, Atletico Madrid and the hefty firepower of Kylian Mbappe and the rest of Paris Saint-Germain. That is a quite remarkable record.

Dig a little deeper and it becomes all the more impressive. The simple fact of the matter is Borussia Dortmund should have conceded an awful lot more goals than they have. Those nine goals for BVB's opponents have come from 187 shots worth a combined 23.02 expected goals (xG). Kobel has made a convincing case to be one of the best goalkeepers in the world this season. If he is preventing 7.09 goals in a competition where only one other player has cleared four, then that suggests not that he is miles clear of the field but that he is on a streak too hot to last. Hummels can't keep making four tackles, five clearances and two interceptions per 90 minutes, can he?

Nothing we've seen from this team in the Bundesliga would lead anyone to think they could be one capable of shutting down Paris Saint-Germain for three hours. "We don't need to sugarcoat anything," said Hummels. "We're playing a very poor Bundesliga campaign." Fifth in the table with 43 goals conceded, a number once more artificially deflated by the excellence of Kobel, without whom the goals against column might have been a lot closer to the 53.27 xG they allowed. Scrub penalties out of the equation and they still have the 10th best defensive record in the Bundesliga. This really isn't a team you would expect to ride a wave of defensive excellence to Wembley.

A settled XI

Or at least, this hasn't been that team for much of the season. The January window had a profound impact on Borussia Dortmund, but perhaps not due to the signing that many would have assumed. Jadon Sancho has had his moments, none more impressive than his bully ball on Nuno Mendes in the first leg of the semifinal. It is Chelsea loanee Maatsen, however, whose contribution has been most profound. Left back had long been a problem position for Borussia Dortmund and those difficulties had not eased with Ramy Bensebaini occupying the spot. Maatsen seemed to solve it in his first game.

Sometimes there is nothing more to functioning defenses than a comfortable fit, as Hummels told CBS Sports Golazo Network. "It's like always, if you have a good working team around you, if your whole team puts effort into the game, it's way easier for you as an individual player to show what you're capable of.

"I know it worked out pretty well this Champions League campaign, especially with the winning goal in Paris, but with Kobel, [Nico] Schlotterbeck, we have a good defensive block in this Champions League campaign. We work together really well. This is always a team effort. If you work well as a team, it's the easiest way to shine as an individual player."

Hummels has done that, so has Maatsen. He just looks the part next to Schlotterbeck and feels at ease in Dortmund's renovated backline. "When I came here, I felt like I've been playing with the guys for many years," he said this week. "I had such a good feeling to come here and felt very welcome, and me and the fans have also had a great connection."

In and out of possession, Dortmund fit together a little more neatly with Maatsen in their side. In 22 league and European games prior to the 22 year old's arrival, Edin Terzic's side were giving up 1.8 xG per game to their opponents. In the 24 since that number has trickled down to 1.53. The story is not quite the same when one isolates European games but the sample size is smaller and on those occasions Dortmund has run into some of the best of the best attacks the continent has to offer. It is perhaps understandable that they pose more of a threat than Darmstadt.

The XI that Maatsen slipped into so easily is now settled. Ahead of the defense Marcel Sabitzer and Emre Can have built a greater understanding, the former bringing the sort of verticality that can allow Dortmund to spring forward. 

Adapting to the toughest games

That approach tends to suit Dortmund but springing forward requires them to be playing as an underdog. As Lewis Ambrose, a football writer based in Germany notes, it is a role that fits them better than the protagonist they are often tasked with being in the Bundesliga. "Dortmund are uniquely terribly set up to play as a big side in the Bundesliga because Terzic tends to be more of a 'vibes' coach than having a strict positional dogma," he says. "So decent and/or brave teams can press Dortmund well and slice through them in transition. Meanwhile smaller sides just sit back and Dortmund struggle to break them down."

Perhaps only once in this competition have Dortmund faced an opponent who they might be labelled favorites to beat. Even then, Sancho's early goal in the second leg created a game state where it made sense for Terzic's side to hold out away to PSV Eindhoven. In that game, as in others on their run to Wembley, they seemed to be at ease with their backs to the wall.

Circumstances may push Dortmund into defending but they do so in a slightly more assertive, robust manner than they did earlier in the season. Just compare their defensive shape from their first meeting with PSG, the opening match of their group stage campaign, and the second leg of the semifinal.

In early games Dortmund drifted across the pitch in their defensive assignments. They didn't then and don't now press with the ferocity of Jurgen Klopp's team. In 2016-17, when Thomas Tuchel was carrying on the work of his predecessor, BVB averaged 7.95 passes allowed per defensive action in the Champions League. This season that number is 13.9. The stretched lines visible above, rarely a precursor to great defense, are even harder to sustain if every player is not hurtling towards the ball with maximum energy.

When these sides met for the fourth time, Dortmund's shape could hardly have been more impressive. On the occasion below the defensive line might be as high as it was on their previous trip to the Parc des Princes -- in general Terzic's backline has crept up the field as this competition has gone on -- but there is none of the space between the lines from that first encounter. Dortmund are going to force their opponent wide, launching the sort of crosses that are just what Hummels and Schlotterbeck want to face. That is if Real Madrid can get those deliveries into the box anyway.

With the ball at Marquinhos' feet in the right half of the pitch, Dortmund left winger Karim Adeyemi has dropped back, ready to turn the back four into a five when required. He and Jadon Sancho on the opposite flank would work themselves into the ground to offer support to their full back. That simply is not going to happen in the Bundesliga to anywhere near the same extent.

The fastest player in the Champions League, moments after the screengrab above he would be hurtling forward to force Marquinhos into a loose ball. PSG would thump the ball high and the surprisingly springy Maatsen would rise highest to flick to safety. Adeyemi's burst was a valuable defensive tool, robbing Achraf Hakimi the chance to get one on one with Dortmund's full back. If PSG were going to advance the ball into more dangerous positions they would need to drag more players out wide, in the process making it more straightforward for Hummels and company to deal with the balls that came into the box.

Good players or good fortune?

Time after time, that was what the veteran center back did. His season was a masterclass of active defending, a three time man of the match including both legs of the semifinal. Ball comes towards Dortmund danger zone, Hummels takes it. The best teams stop attacks at source but at least the threat was quelled.

Reflecting on Hummels' qualities, Kobel told CBS Sports Golazo Network: "The timing he has, the knowledge of the game: sometimes it feels like he sees the situation before it happens. He's always there at the right time. With the experience he built up over the years, he's no stranger to big games. Those are the games where he grows."

For his part, Hummels understands that it isn't down to a 35 year old World Cup winner to just rise to the moment but to bring the best out of those around him. "The good thing is I now have the experience of these games, but I have to be honest," he told CBS, "when I first played the Champions League final or World Cup final, it was really overwhelming. It's a different feeling.

"The semifinals at this stage are big, but it's way bigger when you head to the final, when you know the whole world is watching and everything is at stake in this 90 minutes. I try to talk to the guys who may have this feeling. If it comes, just try to find your way into the game so it feels natural. 

"We all know the feeling of being on the pitch, 11 vs. 11, 90 minutes, this doesn't change. The sooner you get in your natural feeling the better. I know about that, I hope the guys don't get overwhelmed by that feeling. I'm sure most of them will feel it, but it's a great feeling. These are the games you dream of as a child. When it comes to reality you have to grab the opportunity."

Whether the opportunity will be there to be grabbed on Saturday is up for debate. The harsh reality is Dortmund did defend well in both legs against PSG and still gave up a combined 4.95 xG without conceding. Hummels and Schlotterbeck have quite excellently marshalled their penalty area -- the team as a whole has blocked 3.6 xG worth of shots this tournament -- but there is only so much pressure even the very best defenders can cope with. If Goncalo Ramos or Mbappe had had their shooting boots, it would be Les Parisiens in the final. If Olivier Giroud had his Dortmund might have been out of the Champions League before Christmas.

For all the off ball excellence of Kobel, Hummels and Maatsen, to name but a few, the fundamental truth is that this team are at Wembley because their opponents have fluffed their lines on the biggest occasions. Maybe there is something magical about this season that means that will continue against Real Madrid but it seems a long shot. Then again so was Dortmund getting this far in the first place.