It is reaching the point where it may be prudent for Borussia Dortmund to ask their players to retrace their steps over the past few months and find out if any of them have walked underneath any ladders or crossed paths with a black cat. Or maybe Jürgen Klopp could channel his inner Barry Fry and attempt to get rid of the curse that appears to have gripped Dortmund by urinating in all four corners of the Westfalenstadion. Given the state of Dortmund’s luck this season, it could be worth a try.

The latest blow came when Marco Reus, the star of the Dortmund team, injured his right ankle in Saturday’s frustrating 2-2 draw at Paderborn after the winger was caught by a heavy challenge from Marvin Bakalorz. Klopp could not hide his dismay. Dropping back into the bottom three after letting a 2-0 lead slip was one thing but accepting that Reus was facing another spell on the sidelines was not easy.

“It is very difficult to process the fact that Marco Reus could again be ruled out, more difficult than dealing with the draw,” Klopp said, and his worst fears were confirmed when it was announced that Reus, who missed the World Cup with an injury to his left ankle, will not return until the new year. If there is one consolation for Dortmund, it is that Reus’s injury may persuade his suitors to hold off from trying to sign him in the January transfer window. Yet Arsenal will also be relieved that Dortmund will not have Reus available for their Champions League group match at the Emirates on Wednesday. He is one of several Dortmund players who will be missing. Their injury list continues to stretch their resources and Klopp’s patience.

It has been a peculiar season for the team who came within a whisker of winning the Champions League two seasons ago, only to suffer a last-gasp defeat against Bayern Munich at Wembley. A team of their quality should not be in the relegation zone as December approaches but Dortmund, bafflingly, are 16th, two points above Stuttgart in last place. They have won once since their second match, lost seven times and their goal difference is minus five. Pierre-Emerick Aubameyang is their top scorer with four goals. Yet here is where it gets really strange: as bad as Dortmund have been domestically, they have steamrollered their opponents in Europe and they will win Group D with a game to spare if they draw with Arsenal.

Neven Subotic, their Serbian centre-back, is as perplexed as anyone about the discrepancy between their domestic and European form. “It’s very strange indeed,” he tells the Guardian. “We had games where we were better than the opponent, where we started the game off well, but we just couldn’t put the ball in the net and in football sometimes it ends up going the wrong way and that’s what happened a bunch of times when we had a bunch of chances where we couldn’t score and the opponent scores with half a chance.”

Subotic spoke a lot about luck, even when explaining why Dortmund have a 100% record after their opening four group matches. They have scored 13 goals in those four matches, which is two more than they have managed in 12 Bundesliga matches, and they have conceded once but Subotic believes the difference is simple: always scoring first in Europe has allowed them to relax and play their natural game.

“Anderlecht, Arsenal and Galatasaray had at least one good chance per game and didn’t score a goal,” he says. “I think the same chance in a Bundesliga game, the opponent scores the goal and immediately the game changes and we cannot play with the same dominance because teams then have to risk less.”

Dortmund were at their exhilarating best when they beat Arsenal 2-0 at home in September. Arsène Wenger’s side were blown away by the speed and incisiveness of their attack and it was a night when Arsenal were fortunate the scoreline was not more embarrassing. It is why Dortmund are not panicking about their lowly position yet.

“I think that’s key – not to start changing everything, to change the system, to change the coach, to change too many players,” Subotic says. “I think that’s the wrong way to go at it. We stayed faithful to our way and our concept. In the games even after we lost, we had good games, we just couldn’t score a goal or we would get a shot in early from the opponent, and it would make the really hard for everybody.

“But we know what we need to work on is staying focused and putting the plan that we have on to the pitch, obviously with an opponent who doesn’t want us to put our game on to the pitch, and I think that’s the game. Who doesn’t let the opponent do what they want to do? We’ve done well at that. We played our game and we shut down many of the opponents but the biggest problem was that we couldn’t score.

“We’ve always had the same plan and we have good players and we have a great coach and great fans. We couldn’t really explain what was going on, so we knew we had to stick to our plan, because eventually we knew it would work out. We know and we believe in the system.”