Arsène Wenger faces a selection crisis for Arsenal’s opening Champions League match against Borussia Dortmund on Tuesday, having travelled to Germany with only three senior defenders.

The manager knew Mathieu Debuchy would not play against the Bundesliga runners-up because of a suspension for his sending-off against Besitkas in the play-off second leg. The right-back is now a long-term casualty, having badly damaged an ankle against Manchester City on Saturday and he has been joined on the injury list by Nacho Monreal, who has a minor back problem.

Wenger also reported that the 19-year-old Calum Chambers was a doubt because of tonsillitis – he faces a fitness check in the morning – and it has left the manager with only Per Mertesacker, Laurent Koscielny and Kieran Gibbs as recognised, established defenders. Gibbs, who has a history of injury problems, has only just recovered after his latest muscle strain. Chambers did not train in London on Monday morning before the squad flew to Germany.

Wenger has included the 19-year-old academy right-back Héctor Bellerín in the travelling party but he is reluctant to pitch him into such a difficult game. Bellerín has made one brief appearance for the club as a substitute in the Capital One Cup.

It is more likely that he will ask the midfielder Mathieu Flamini to deputise at right-back if Chambers does not make it. If Chambers is fit, Wenger could play him alongside Mertesacker in central defence and switch Koscielny to right-back. Chambers, who had played only at right-back for his previous club, Southampton, has impressed Wenger in central defence.

“The Debuchy injury has put us in a position where we do not want any more,” Wenger said. “He is out for a longer period. How long, we don’t know yet. Hopefully, we have good news after the scan that he had today. Monreal didn’t travel and we have a little problem with Chambers. We’ll assess him. At the moment, he’s 50-50. Monreal is a back problem. He should be available on Friday. Yaya Sanogo [the striker] also stayed at home with a little hamstring problem.”

On Bellerín, Wenger said: “He’s a boy with personality. He’s not fazed by the pressure. That’s important when you’re a young boy. His transitional game is fantastic. He’s quick and his final ball is good. He lacks a bit of experience but he’s very dangerous.”

Wenger’s summer transfer policy with regard to defensive additions was placed under scrutiny. He had said that he would sign another centre-back if Thomas Vermaelen left, which he did, for Barcelona. Wenger explored a host of options, including Dortmund’s Sokratis Papastathopoulos but came to consider Chambers as a solution in central defence, as well as right-back.

“We have Chambers who can play in different positions, Monreal who can play centre-back and Bellerín, who I think is now ready to play,” Wenger said.

Wenger’s squad contains three of Germany’s World Cup winners – Mertesacker, Mesut Özil and Lukas Podolski – and he said there would be increased pressure on them to perform in Dortmund. Özil is under particular scrutiny after a lacklustre showing against City.

“It is always a pressure when you come back to your country,” Wenger said. “The attention is bigger. Our German internationals played in the World Cup final in Rio on 13 July and they came back to training with us on 11 August. It was important for me that they would recover. They have been training for one month and they haven’t reached 100% physically. But they’re close.”

Mertesacker said: “This first Champions League game will show where we’re at. The group is tough and we have to show from the start we are ready and focused.”

Arsenal have not lost an opening Champions League group tie since 2003 – against Internazionale at Highbury – and they face a Dortmund team with selection issues of their own. Jürgen Klopp, the Dortmund manager, will be without the injured Mats Hummels, Ilkay Gündogan, Marco Reus, Jakub Blaszczykowski, Nuri Sahin and Oliver Kirch.