PARIS- Two former Champions League winners Manchester United and Borussia Dortmund who have both been having trouble in their domestic leagues suffered differing fortunes on Tuesday in their Champions League last 16 first leg ties.United's woeful season, in manager David Moyes's maiden campaign, took another turn for the worse as they went down 2-0 to Greek champions Olympiakos in Piraeus and the measure of the task awaiting the English champions at Old Trafford in three weeks time is that only one team has come back from a two goal first leg deficit before in the Champions League knockout stages. United's failure to score left English clubs goalless in this round, with both Arsenal and Manchester City failing to score last week although Chelsea can set that right agaisnt Galatasaray on Wednesday.Dortmund -- beaten finalists last season -- have also struggled to impose themselves in their league, they trail Bayern Munich by 20 points, but they can probably look forward to the quarter-finals of this competition as they beat Zenit St Petersburg 4-2 in Russia. Manchester United had been just one of three teams coming into the knockout stages not to have lost thusfar in this season's competition but goals from veteran Alejandro Dominguez and a stunning curling effort by Costa Rican Joel Campbell -- on loan from Arsenal -- ended that record.United can take heart that they have won 13 of their last 15 home games in the knockout stages of the competition although their last defeat was at this stage last year to Real Madrid. Moyes, who was the personal choice of Alex Ferguson to replace him when he stepped down at the end of last season, admitted it had been a woeful performance. "It's the worst we've played in Europe, that's for sure," said Moyes, whose side are struggling to even make the competition next season as they trail fourth-placed Liverpool by 11 points."It was a really poor performance. We never really got going from the start and we didn't deserve anything because of the way we played. I take responsibility. It's my team. We didn't play well tonight and we have to play better, but we know that we can do." His Olympiakos counterpart former Spain and Real Madrid midfielder Michel was delighted with the result but said there was still a long way to go if the Greek side were to reach the quarter-finals for the first time since 1999."Today's match shows we've done a very good job. I'm obviously very happy with this match, but most of all, I'm proud of my players," said the 50-year-old. "But if somebody says that 2-0 is enough to qualify, he's probably wrong. We have a 2-0 lead against Manchester United, which means nothing." United midfielder Michael Carrick -- who was nutmegged by Campbell in the lead up to the second goal -- said that while the performance hads not been a good one he felt they could turn it around at Old Trafford in three weeks time."We've lost a game. We came here hoping to win but we are not out of the tie," he said. "You're looking for me to blame someone but everyone at the club is judged by results." Dortmund had Zenit on the back foot from the start of their game as the hosts looked like a side that hadn't played a competitive match since December 6. First Marco Reus set up Henrikh Mkhitaryan and then he scored himself in the first five minutes. Although Zenit restored a bit of pride in the second-half with two goals they were counter-balanced by Polish striker Robert Lewandowski scoring a brace to give the Russian side an almost impossible task in three weeks time.Dortmund's performance was especially pleasing to their coach Jurgen Klopp as it came just days after an insipid performance in a 3-0 defeat to Bundesliga strugglers Hamburg. "It was clear to me that my team would produce a reaction," said Dortmund coach Jurgen Klopp. "My team can never be accused of going about their business without showing some character, but we still have work to do in the second leg."