Barcelona coach Pep Guardiola believes the Champions League last-16 has been a graveyard round for previous tournament winners, making him doubly wary of Tuesday's first leg at VfB Stuttgart.
"If you analyse the results you will see that in the last few years a number of champions such as Liverpool and AC Milan have gone out at this stage in the following year," he told reporters.
"It's one of the most difficult ties in the competition. Only Manchester United have survived in the last few years."
Champions Barcelona are firm favourites to overcome Stuttgart, who are ninth in the Bundesliga, but the record books warn of the pitfalls.
Liverpool, who won the trophy in 2005, were dumped out by Benfica in the last-16 the following year.
Barcelona, the 2006 winners, were beaten by Liverpool at the same stage of their title defence and 2007 champions Milan continued the sequence when they were beaten by Arsenal.
United, winners two years ago, ended the jinx by reaching last year's final where they lost to Barca.
Guardiola said the favoured teams all had a hard time in last week's opening four matches and he was always on the lookout for over-confidence.
"It's part of my job," he said.
Guardiola said La Liga leaders Barcelona did not play well against Racing Santander on Saturday despite winning 4-0 and he accepted criticism from former player and coach Johan Cruyff.
"He's an inspiration for me," said Guardiola who played under the Dutch great.
"I wouldn't be here if it wasn't for him, he has taught us so much. I listen with attention to everything he says.
"It's important to start well," added Guardiola. "If you lose the ball the Germans will murder you on the counter-attack."
Argentina striker Lionel Messi said he was unconcerned about adding to his tally of two Champions League goals this season.
"It's important for the team to win. It doesn't matter if I score or not," said Messi who notched nine last season. "If I score, good, if I don't, nothing happens."
Stuttgart, 15th in the Bundesliga when the draw was made in December, have jumped up the table after seven wins in eight games under former Tottenham Hotspur coach Christian Gross.
"I came here to help the team avoid relegation," said the Swiss. "We also had one game to go in the group stage, we had a chance to go through, took it and now we are going to play against the best team in the world.
"We can play with our minds clear, we have nothing to lose. We don't have any pressure on our shoulders," added Gross.