The outcome was far better than the performance as Barca claimed a point from arguably their toughest game of the group stage, but manager Ernesto Valverde will know his team needs to improve significantly all over the pitch.
Here are the key takeaways from this Champions League opener.
Ter Stegen to the rescue
This was a far from convincing performance from Barcelona, who created no major chances of note and were indebted to a combination of poor finishing, a touch of fortune when Julian Brandt’s thunderbolt shot crashed onto the crossbar and, above all, some excellent goalkeeping from Marc-Andre ter Stegen.
Back in his native Germany, the keeper produced several super stops highlighted by a magnificent diving effort full stretch to his left to palm away Marco Reus’s penalty midway through the second half (although, it must be acknowledged, the penalty really should have been retaken because ter Stegen had advanced halfway to Moenchengladbach before it was taken).
The outstanding display felt like something of a statement from ter Stegen, who has attracted big headlines in Germany over several months for national team coach Joachim Low’s refusal to promote him ahead of Manuel Neuer as Germany’s first choice.
Overhauling a legend and team captain like Neuer is no easy task, especially when he carries so much support within Germany as a star player for the country’s most popular club Bayern Munich, but ter Stegen cannot have done any more to state his case. Now all he can do is wait until next month’s internationals, and keep his fingers crossed.
Away woes continue
Aside from ter Stegen, there were very few bright spots to Barcelona’s performance. They were continually vulnerable at the back, with Nelson Semedo suffering a torrid night against Jadon Sancho and the centre back duo of Clement Lenglet and Gerard Pique regularly getting caught on their heels.
The midfield trio of Sergio Busquets, Arthur Melo and Frenkie de Jong kept the ball well at times without offering any penetration, and were regularly exposed by Dortmund’s swift breaks from defence – although that was less evident after de Jong moved to the pivot position in place of Busquets.
Up front, Antoine Griezmann worked hard up and down the left wing but rarely threatened goal, while Luis Suarez was starved of service and teenager Ansu Fati was handed a dose of reality after the magic of his previous performance against Valencia.
It all added up to a pretty mediocre showing which continues the team’s troubles away from home, leaving Ernesto Valverde’s men with just one win from their last eight road trips. If they don’t find a way of delivering more effective performances on their travels soon – starting at Granada on Saturday – they will struggle to claim any meaningful silverware this season.
Messi back in business
Aside from ter Stegen, the only real positive on the night for Barca was the return to action of Lionel Messi, who made his first appearance of the season after recovering from a calf strain by replacing Fati after an hour.
Although there were a few shimmies and feints to send a reminder of Messi’s brilliance, in truth he wasn’t able to exert a big influence on the action as Dortmund pushed harder for a winner, and his only sight of goal was swiftly snuffed out by a solid block as he latched onto a deep cross with the last touch of the game.
But expecting Messi – or any other player – to be performing at their peak after not playing any competitive football for more than two months and only completing two full training sessions would be wholly unrealistic, and Barca fans should just be grateful to see their icon back on the pitch rather than worrying too much about how he played.
The next decision to be made by Messi and Valverde – presumably after discussion together – is whether he will start at Granada on Saturday or wait until next Tuesday night’s home meeting with Villarreal.
The Portugal skipper and his Barcelona and Argentina rival have each claimed the prestigious award on five occasions, but 34-year-old Ronaldo is not satisfied with that.
Speaking on ITV’s Cristiano Ronaldo Meets Piers Morgan, the 34-year-old Juventus superstar said: “I would love it, and I think I deserve it.
“Messi is a fantastic guy, a fantastic player. He’s in the history of football – but I think I have to have six or seven or eight to be above him.
“My relationship with him is, we are not friends, but we have shared this stage for 15 years. I have a good relationship with him and I know that he has pushed me to be a better player and I have pushed him to be a better player as well.”
Serial winner Ronaldo, who agreed that Messi is the best he has played against, hopes to be remembered as one of the best – if not the best – footballers the game has ever seen.
He said: “I’m sure I’m in the history of football for what I have done and what I’m continuing to do, but one of the best players in history.
“For me, the number one in history, but for some fans, if the number one is another one and I’m second, it doesn’t matter.
“I know I’m in the history of football as one of the greatest ever.”
The former Manchester United and Real Madrid player has five Champions League titles to his name and has led Portugal to Euro 2016 and Nations League glory, and the 145 individual records he has amassed along the way continue to fuel his quest for more honours.
He said: “It’s part of my sacrifice, my obsession to win, to have success. When I say success, I have worked for that. Talent is not enough, I dedicate so much that this is part of me, records are part of me.
“I don’t follow the records, the records follow me. I’m addicted to the success, and I don’t think it’s something bad, I think it’s good. It motivates me. If you’re not motivated, it’s better to stop.”
The Madeira-born striker was moved to tears when shown footage of his late father Jose Dinis Aveiro, who died of liver failure as he was making his way in the game, and he revealed his gratitude to his mother Dolores for her support throughout his life to date.
He said: “My mum was the pillar of the family. What I have today, it’s in big part from her.”
Ronaldo, who has four children, found himself thrust into the limelight for the wrong reasons last year when he was accused of rape and although no charges were ever brought, that had an impact on him, his girlfriend Georgina Rodriguez and their family – in particular his mother.
He said: “I’m not going to forget that 2018 probably was the most difficult year of my life in terms of outside football.
“My mum sometimes was very nervous and I said, ‘Mum, relax. You know the son that you have at home, relax, nothing is going to happen. Trust me’.
“But she was nervous, she is old. She is nervous at games – imagine the personal stuff of her son, thinking about jail, rape, this kind of stuff. It’s hard for an old person.
“But at the end of the day, it was good. The law did the job it should do and I’m happy, of course.”
Jurgen Klopp questioned the awarding of a penalty to Napoli which he felt proved decisive as Liverpool started the defence of their Champions League crown on a bum note.
The Reds lacked a cutting edge but would have been worthy of a point at the intimidating Stadio San Paolo, only for the Group E opener to hinge on Jose Callejon being upended in the area by Andy Robertson.
Dries Mertens converted from the spot in the 82nd minute before Virgil Van Dijk lost the ball on the edge of the area in stoppage time, allowing former Tottenham striker Fernando Llorente to seal a 2-0 win for Napoli.
Liverpool manager Klopp said: “When we conceded to go 1-0 down that was the game changer. We have to accept the result.
“We are really critical of ourselves but it was not a really, really bad performance, it was a game which we could have won at Napoli but we didn’t because we didn’t score.
“We wanted to have at least a point and we didn’t get that because of the penalty. I’m pretty sure there are different views on that situation but when a player jumps before there is contact then it cannot be a penalty.
“But we cannot change that anymore so that’s how it is and now we carry on, that’s it.”
The Reds’ strong appeals for a penalty against Newcastle at the weekend fell on deaf ears but they maintained their 100 per cent winning start to the Premier League season by beating the Magpies 3-1.
Tuesday night’s decision proved central to the outcome but Klopp refused to be too critical of the process involving the video assistant referee.
He added: “I could say a lot of things about it but then I would look like a bad loser. I’m not the best loser in the world but I’m not bad at it.
“It was very decisive in that moment for sure but we can’t change it. As long as human beings make the decisions then there is still potential for (mistakes). The rules are like this and we trust in the rules.”
The visitors, barracked throughout in a hostile atmosphere in Naples, lost the corresponding fixture between the sides last season en route to being defeated in every group stage game away from Anfield.
The Merseysiders managed to pip Napoli to the knockout stages by virtue of goals scored and went on to lift the European Cup for the sixth time in their history.
Klopp believes Napoli are more than capable of going all the way this season.
He added: “They can win the competition. If you have a good plan and good players, which they obviously have, then they can win the competition. We experienced that.
“You don’t have to be the best team in the world to win the Champions League. You have to be there in the right moments and you have to be lucky in some situations.”
Napoli counterpart Carlo Ancelotti welcomed Klopp’s assessment of his side as potential winners.
The Italian said: “If Jurgen Klopp says that we have the ability to go on and win the Champions League then I say to him, ‘thank you very much’ because he’s a coach that knows football inside out.
“But there is still a very long way to go. Our first objective is to try to get through to the knockout stages.”
Provided by Press Association Sport