André Villas-Boas accepted his responsibility to coax "concentration and focus" from his beleaguered players, after Chelsea lost to a stoppage-time Bayer Leverkusen goal that left their qualification for the knockout phase of the Champions League in doubt. The Londoners must win or keep a clean sheet against Valencia at Stamford Bridge on 6 December to guarantee progress, most likely in second place in Group E behind Leverkusen. Recent form suggests they may struggle to do either. They have lost three of four Premier League games, leaving them 12 points behind the leaders, Manchester City.

"Confidence is low, but they expect the manager to inspire them," Villas-Boas said. "That's my job, to motivate and inspire these people. Their talent is immense, the work rate is good but the responsibility is mine. I have to motivate them to get a win against Wolves [on Saturday] and then against Liverpool in the Carling Cup [on Tuesday]. We have two games at home and need to get the focus and concentration right.

"We're in a negative spiral of results. The team want to get out of it desperately and the only thing we can do is work even harder to achieve that. This is a critical moment for our team and we will need the fans behind us. We were good and solid here but, in two situations from set pieces, we left our back exposed.

"Leverkusen hit the woodwork with the first and scored with the second in stoppage time. Little details are deciding our fate at the moment, but we're all committed to this squad and these players, we believe in their talent. We have to find a way out."

Chelsea had cause to feel aggrieved that Lars Bender was not penalised for bringing down Didier Drogba in the penalty area, though Leverkusen's Michael Ballack said that the German team had been fortunate only in the timing of their winner.

"It's always a little bit lucky if you score in the last minute, but we believed," the former Chelsea midfielder said. "A draw would have been deserved but we got the victory. They are not in the best moment but of course, in the end it was a little bit lucky. Every team has difficult moments, and they are in one now. But I know their players are very competitive and I think they will come back. They have a strong side and they will be back."

Ashley Cole may not return against Wolves, the England full‑back having damaged an ankle in training. He was rated "60-40" by his manager to play. After Wolves and Liverpool, Chelsea face key games against Newcastle and Manchester City in the league and Valencia in Europe.

"At the moment the explanation is we need to get the focus and concentration right," Villas-Boas said. "If that's what is making the difference, then that's what we need. Focus is difficult.

"We need to train, improve the quality of training, make them concentrate harder – not that we've not been doing that in the past – but that's what we have to do. We need to work to keep our faith and get things right, and get the wins this team deserves.

"This result was unfair in the end. The game was heading for 1-1 and we had a good share of the chances created, but that's not what matters. What matters is that Leverkusen have taken three important points to change the nature of the group.

"Now we go into the final game against Valencia to decide our qualification. They are a team on the up and we'll need Stamford Bridge behind us to get the intensity right. It's in our hands to qualify and we expect to do our job. That's our responsibility, and we don't want to let the fans down."