Brendan Rodgers agrees that facing Borussia Dortmund in front of their famous "Yellow Wall" of fans on Tuesday is the "acid test" of Celtic's ability to compete in the Champions League.

But he is confident that improvements to his squad this summer have shown they can "bring our game to the next level".

Celtic have headed to Germany to face last season's beaten finalists on the back of a run of nine straight victories this season, including a 5-1 thrashing of Slovan Bratislava in their Champions League opener in Glasgow.

Dortmund eased aside hosts Club Bruges 3-0 but suffered a 5-1 Bundesliga thumping by Stuttgart before recovering with 4-2 defeat of Bochum.

Asked if this was the acid test for his Scottish Premiership leaders, Rodgers replied: "I think this level is about as much about the head as it is about the skill. I don't doubt that with this team.

Celtic fired six goals without reply away to St Johnstone on Saturday, but it was to a pre-season when Rodgers lined up matches against some top opponents where he looked as ideal preparation.

"I track it back to pre-season," he said. "The games that we played there, played some big teams and how we wanted to play at this level.

"We got off to a very good start in the last round, so we come here to a stadium very much like Celtic Park in that they breath football and we're very excited by the challenge.

"We are under no illusions that we are up against a team who are challenging at the very top of elite football, but for us I've always said, whether domestically or away in this competition, it is about making us very difficult to play against with and without the ball.

"Offensively, Dortmund are very good. They lost some players in the summer, but I look at the team and they have some fantastic players in that middle to top area so will put you on the back foot at times.

"It is a top side with top players and we have to be right on it to get a good performance and result."

Dortmund head coach Nuri Sahin is not underestimating Celtic's challenge.

"I don't think it's fair to call them underdogs to be honest," he said.

"You're talking about a team who haven't lost for many games and haven't even lost a goal in their league. They were very dominant in their first match in the Champions League.

"They are a very prestigious club with amazing talent in their squad and a fantastic coach. It will be a challenge for us, but at the same time a big challenge, a huge challenge, which they didn't have this season, playing in our stadium.

United States centre-half Cameron Carter-Vickers is again not available for Celtic through injury and has not travelled to Germany.

English winger Jamie Gittens and Norway full-back Julian Ryerson, who both came off for Dortmund with injuries against Bochum, trained on Monday, as did Austria midfielder Marcel Sabitzer, who missed that game.

Filippo Mane, the 19-year-old centre-back, is also back training along with 18-year-old left-back Almugera Kabar, who trained with a mask due to a broken nose.

However, Sunderland-born United States midfielder Giovanni Reyna remains on the sidelines.

Borussia Dortmund head coach Nuri Sahin: "If you really want a name, I'm a big, big fan of your striker.

"Furuhashi is not a typical striker like we are used to, a big one. But he is very smart and I really like how he moves off the ball, the timing of his runs. I see a very smart guy there tactically."

Celtic midfielder Arne Engels: "It's always amazing to be here and also to come back because I played here a few times. It's an amazing stadium and it's always positive to play here.

"If you can play at Celtic Park, you can play everywhere. If you don't have the belief then you are better not to come and say it's 5-0 for them. We want to come here and win like every game."