BRENDAN RODGERS, the Liverpool manager, has promised to treat Champions League outsiders Ludogorets with the utmost respect when the little-known Bulgarian side make their debut in the group stage of the competition at Anfield tonight.

"We'll respect them like we would if we were playing Real Madrid," Rodgers said.

Saturday's 1-0 home defeat by Aston Villa should help the Barclays Premier League side avoid any complacency and the manner of it convinced Rodgers that his new-look defence must improve. Liverpool have kept a clean sheet in only one of their four games this season and two in 13 going back to last March.

"We need to be better in those areas," Rodgers admitted. "We were disappointed with how we conceded a goal at the weekend. We had five players making their Anfield debut and the cohesion does take a little time."

It will be Rodgers's first match in charge for any Champions League tie and Liverpool's first since December 2009. "Five years is a long time, probably too long," he said.

"When I came here my main priority was to get the club back to this level. We want to be at the elite level and the Champions League is that."

Asked about Ludogorets, Bulgarian champions for the past three seasons, who came through three qualifying rounds, he said: "They play an open, attacking style and they'll come here with confidence. They've worked hard to get here and we know they'll be excited about coming to Anfield, one of the most iconic stadiums in the world."

Rodgers confirmed that the Slovakian centre-half Martin Skrtel will not be ready to return, but there are no new injury concerns.

Arsene Wenger, the Arsenal manager, however, will be without right-back Mathieu Debuchy for a "long period" of time and is struggling with defensive options for their group opener against Dortmund. Debuchy suffered ankle ligament damage in the 2-2 draw with Manchester City on Saturday and is undergoing more tests.

Yaya Sanogo stayed in London because of a hamstring problem, and Wenger will be without injured left-back Nacho Monreal while Calum Chambers, who missed training yesterday morning, is being treated for tonsillitis and has a "50-50 chance" of playing. "In defence we of course have the Mathieu Debuchy injury, and that puts us in a position where we do not want more," said Wenger.

"Monreal didn't travel and Chambers is 50-50. Debuchy is out for a longer period. We don't know how long. Sanogo stayed at home with a little hamstring problem."

Wenger may now be forced to start the 19-year-old right-back Hector Bellerin. "We have as well Bellerin, who I think is now ready to play."

Dortmund and Arsenal are no strangers, having met last season as well as in 2011 in the competition with upbeat Wenger heaping praise on his German counterpart Juergen Klopp.

"I have great respect for Mr Klopp. He rose up very quickly in his career and inspired Dortmund," said Wenger. "What does he do better than me? Maybe a lot of things. But I love to see his squad playing dynamic and attractive football. I like it."

Klopp himself was full of praise for the returned attacking midfielder, Shinji Kagawa, who signed for the club for a second time, from Manchester United, in the summer. Klopp warned, though, that the Japanese playmaker is not an automatic starter against Arsenal, despite scoring on his first game back on Saturday.

The 25-year-old, who spent two disappointing seasons at United after winning back-to-back German league titles at Dortmund in 2011 and 2012, scored one goal and helped set up the other in their 3-1 win over Freiburg.

"For a first game back it was an extraordinary one for him on Saturday," Klopp said. "A decision whether he will play tomorrow will be taken tomorrow morning. Those who saw Arsenal here last year know very well they can also play defensive football and switch their game very quickly.

"We should play according to our natural virtues and take some tactical measures to keep them at bay."