Borussia Dortmund Find Their Attacking Groove in Hammering of Legia Warsaw

"It was only against Legia Warsaw."

That mantra will probably reverberate around Borussia Dortmund's training facilities after Wednesday's thrashing of the Polish champions in the Black and Yellows' UEFA Champions League opener. It was only Legia, but any 6-0 win away from home in Europe's premier competition should be celebrated.

It was the Ruhr side's highest-ever win in the Champions League, as the club's website pointed out, and one would be hard-pressed to find another performance as dominant as the one head coach Thomas Tuchel's men delivered in Wojska Polskiego Stadium.

The hosts, of course, are no measuring stick for future success. Struggling in Ekstraklasa, Legia are 13th of 16 teams after eight matchdays. The capital club was overwhelmed from the first to the final whistle, leaving acres of space for Dortmund even when defending set pieces.

Having issued that caveat, there are still some things we can take away from an easy win for the Black and Yellows.

After they had struggled to create dangerous situations both against Mainz 05 and RB Leipzig on the Bundesliga's first two matchdays, Dortmund got their creative woes off their chest with a sparkling display of playfulness. 

Despite or precisely because Tuchel opted for no fewer than four players who made their Champions League debuts in midfield, his side attacked with a vigor and carefree attitude that made for a thoroughly enjoyable watch even though the game was over after just 17 minutes: That's how long it took them to take a three-goal lead.

The 43-year-old gave a full club debut to Raphael Guerreiro in central midfield, as well as a season debut to Christian Pulisic on the right wing. With Andre Schurrle injured, Ousmane Dembele manned the left wing, while Mario Gotze played next to Guerreiro.

Julian Weigl was the lone holding midfielder in a clear 4-1-4-1 structure that allowed Dortmund to keep the ball among themselves at will, as evidenced by the 68 per cent possession they had, according to German sport magazine Kicker. Even more impressively, they had fewer misplaced passes than their opponents despite their dominance on the ball.

After a structured setup was missing against Mainz and worse against Leipzig, where central midfielders Weigl, Gonzalo Castro and Sebastian Rode failed to advance the ball toward the final third, Dortmund had no such problems against Legia.

Weigl was the main hub in the buildup phase, completing an astounding 95 of his 101 passes, per WhoScored.com—Warsaw only completed 210 as a team, per Kicker.

The graphic below shows the 20-year-old's importance in his Champions League debut, but also take a look at all the triangles Dortmund formed on the pitch, as they helped the team combine their way through a spinney of Legia's deep-sitting defenders:

The hosts had no answers to all the problems the Black and Yellows posed and allowed a barrage of chances—stat provider Opta noted that only Juventus fired off more shots in an away game in the Champions League than the 30 Dortmund managed on Wednesday.

Tuchel told German broadcaster ZDF after the match, per the club's website: 

"

What made us stand out was our desire to play the balls in up top, not waiting but playing the balls in with the necessary sharpness. As for the fact that we set a record with 30 shots on goal, okay. It shows that we were hungry. You could see we were enjoying ourselves out there. We never let up. I'm very happy about that.

"

Indeed, it would've been easy to take the foot off the gas and cruise to a comfortable victory after they snowballed Legia in the first 17 minutes.

Gotze opened the floodgates with a strong header from a perfect cross; it was the kind of goal that makes one wonder why the 24-year-old so often struggles playing up front for the national team.

Centre-backs Sokratis Papastathopoulos and Marc Bartra got in on the action following set pieces, with the Catalan's goal reflecting especially poorly on the hosts, seeing as he poked in the third rebound Dortmund won after Legia goalkeeper Arkadiusz Malarz saved a Guerreiro free-kick.

The Black and Yellows could've made the half-time scoreline much more ugly for Legia had Dembele and Pierre-Emerick Aubameyang not missed golden opportunities to add more goals.

Guerreiro added the fourth with a cool finish just six minutes into the second period, slotting home a blocked effort from Dembele. 

The pick of the litter, however, was the fifth goal. Shortly after his introduction into the game, Emre Mor displayed his incredible technical abilities with a magical piece of skill to retain possession in midfield before playing in Pulisic, who had moved to the left wing halfway through the second half.

The 17-year-old United States international played a perfectly weighted first-time ball across the face of goal toward Castro, who entered the pitch at the same time as Mor, leaving all but a tap-in for the 29-year-old. 

"

Pulisic with a fantastic first time cross for Castro who puts Dortmund up 5-0 https://t.co/E5iXBECJpA

— Nats Abroad (@NatsAbroad) September 14, 2016"

The former Germany international then played in Aubameyang for the sixth and final goal, Africa's Footballer of the Year cleverly chipping the ball over Malarz with his weaker foot.

One could think it's difficult to single out one man as the best player on the pitch in such a rout of hapless opponents, but it's not. Guerreiro stood out even with five or six of his team-mates playing at their highest capacity.

The Euro 2016 champion put on an all-action show with nifty dribbles, assured passing and dangerous deliveries from set pieces, thoroughly deserving his high marks. Both Kicker and ESPN FC's Stefan Buczko rated his performance at nine out of 10.

The 22-year-old summer signing called his Champions League debut "a dream come true" in an interview with Matthias Dersch of local paper Ruhr Nachrichten (h/t BVB.de).

After impressing at the Euros at left-back for Portugal, most fans thought Guerreiro would come to the club as competition and, ultimately, a replacement for captain Marcel Schmelzer, but he's been used mostly in midfield so far.

JANEK SKARZYNSKI/Getty Images

"I've always played as a left-back," he told Dersch after the match on Wednesday. "I also came to Dortmund in the belief that I would continue to play there. But I'm at BVB to learn things. If the coach puts me in midfield, then I will try to do the best I can."

This writer took a look at how the former FC Lorient man might best fit into Tuchel's plans in an earlier piece, and his performance in midfield against Legia shouldn't come as a surprise: He's got the technical qualities, the passing range and the tactical understanding to excel in that role.

With Dortmund's attack exploding after a wobbly start to the campaign, expect Guerreiro to keep his spot as a creative force in central midfield for now. Especially in games where they can expect to see most of the ball, he is clearly a superior option to Rode or Castro.

It was only Legia, yes, but even a win against the weakest of opponents can serve as a catalyst for the rest of the season.

Lars Pollmann also writes for YellowWallPod.com. You can follow him on Twitter.