"Dortmund can beat Barcelona at home" - Witsel

The 30-year-old played 78 minutes of BVB's 4-0 victory at home to Bayer Leverkusen on Saturday, a match which Dortmund had to work hard to take away from their opponents in a clinical second half display.

The result aside, the fact that Dortmund had to dig deep despite only having 37.3 per cent of possession served as ideal preparation for facing the 2015 European champions, who are famed for their ball-hogging style.

"It's always hard against Leverkusen because they press all the time," Witsel told bundesliga.com after the game. "They're up there with Leipzig as the best team in Germany when it comes to pressing. But in the end we won 4-0, we played on the counter. Sometimes you have to win games by playing like this."

The result leaves Dortmund in second place in the Bundesliga standings, one point behind leaders Leipzig and one ahead of Bayern Munich. And having advanced to the DFB Cup second round last month, they are looking to make an equally successful start to their Champions League campaign this week.

"Personally I've never played against Barcelona so it'll be my first time," said Witsel. "It'll be a tough game because it's Barcelona. But we have to believe, play hard, prepare for the game like it's just another Bundesliga match and give everything out on the pitch. I think at home we can do it [beat Barcelona]."

Watch: How Witsel makes Dortmund tick!

Part of his optimism stems from Dortmund's improved display in terms of their focus, too. After losing to Union Berlin on Matchday 3, captain Marco Reus called on his teammates to "show a different mindset", and the willingness of Lucien Favre's men to adapt to a new playing style against Leverkusen was testament to their doing just that.

"Today I think our mentality [was the key to our win]," Witsel continued. "It's hard to always run after the ball because we're not used to it. We were very good and had good fighting spirit also.

"We can play on the counter sometimes, but most of the time we have to play our usual game. If you want to be champions you have to win this way as well. It was an important sign after the defeat to Union. We've shown we can play nice football, but also that we can be strong defensively, be compact and play on the counter. We have quick players up front who can make the difference."

That is quite the understatement. Reus, Jadon Sancho and Paco Alcacer were devastating against Leverkusen, the trio creating an unstoppable – and crucially - clinical blur of pace, movement, trickery and precision to sucker-punch Die Werkself into submission.

A repeat performance on Tuesday – with Alcacer already on 10 goals in eight competitive outings for club and country this season as he prepares to face his former employers – could set the tone for what is shaping up to be a fruitful campaign.