Chelsea caught out late on

Champions League review: Manuel Friedrich's towering stoppage-time header heaped more pressure on Andre Villas-Boas as Bayer Leverkusen came from a goal down to beat Chelsea 2-1 at the BayArena. Arsenal will top Group F after a Robin VAn Persie brace saw off Borussia Dortmund at the Emirates Stadium.

The Blues looked set for a restorative win and a place in the Champions League last 16 when Didier Drogba drilled home shortly after the break. But their defensive frailties were exposed again in the 73rd minute when a hopeful ball out of the Leverkusen half evaded the Blues' back four and with Petr Cech exposed, Sidney Sam showed great composure to tee up substitute Eren Derdiyok.

With seconds remaining, Freidrich rose higher than Alex and powered a header beyond Cech's grasp to send the Germans top of Group E and into the last 16.

The defeat was Chelsea's fourth in their last seven games and leaves them needing to avoid a defeat or a score draw in their last group game against Valencia, who won 7-0 at home to Genk, at Stamford Bridge to reach the last 16.

Manager Andre Villas-Boas afterwards challenged his side “to go one more step up” in their performances.

He told ITV: "Our focus must be at the moment on Valencia at home. We are still in front of Valencia but it will be a good head-to-head battle, decisive. It's tough for the English clubs at the moment in the Champions League but we have to face it, put on a brave face and get back to the wins.

“We’ve been suffering a lot, conceding a lot of goals, \[but] we haven’t conceded from a corner for a long time — I think that was the first time. We were compact and disciplined in set plays but one detail in the last moment [cost us]. There are no perfect organisations. One small detail makes the whole difference and in this competition you pay heavily.

“We need to get the concentration and focus right. No excuses — if we have to go one more step up that’s what we have to do.”

Leverkusen's Michael Ballack is still backing his former club to come good.

He said: "We are in the next round, but Chelsea have a game at home against Valencia so they still have a good chance. Every team has sometimes a difficult moment and Chelsea is in a moment like this now.

"I know the players are very competitive and I think they will come back. They have a strong side and they will come back."

At the Emirates, van Persie took his 2011 goal tally to 33 goals in 30 matches when heading home Alex Song’s cross before adding a second from close range following Thomas Vermaelen’s flick-on four minutes from time.

A win seemed unlikely for the home side after Dortmund dominated the first half, but they faded in the second period before pulling one back in injury time through Shinji Kagawa.

Robert Lewandowski went close for the homeside on two occasions in the first half, while Roman Weidenfeller denied Theo Walcott in a frustrating opening for the Gunners.

Walcott beat him five minutes before the break but it was ruled out for offside, though the home fans were on their feet four minutes into the second half.

Van Persie was the executioner with a fine header but Alex Song was the creator with a mazy run and scooped cross from the left.

Gervinho was then sent clear one-on-one by Aaron Ramsey, but dithered after rounding the keeper and the chance was gone.

Van Persie (86) sent the fans home happy as he stole in at the back post after Thomas Vermaelen had flicked on Mikel Arteta's corner, although Shinji Kagawa (90) had the last word for Dortmund.

Marseille's shock 1-0 defeat at home to Olympiacos in the night's other Group F clash means Arsene Wenger's side cannot now be caught, though they could yet be joined in the second round by any of their group opponents.

Alex Song said after the game: "We took our time to get going, it was not easy but in the end it was really good and we got the result. We wanted to do well today so we're really happy.

"We showed good character."

Of Van Persie, Song told Sky Sports 2: "He's in unbelievable form. He's a very good player and a pleasure to play with and he shows how good he is in every game. He is very important and we hope he doesn't get injured because when he does, it is very difficult for us. We just need to keep him in good form."