Michael Ballack believes Bayer Leverkusen are capable of putting another serious dent in Chelsea's faltering campaign on Wednesday night.
The Blues will head to Germany in midweek for the latest round of UEFA Champions League fixtures.
Andre Villas-Boas' side sit top of Group E after four games, but they are far from assured of booking a place in the last 16.
Their form has wobbled alarmingly over recent weeks, with three defeats suffered in their last four Premier League outings.
They could also manage only a draw in their last European match away at Genk.
Ex-Chelsea star Ballack believes his former employers could be there for the taking and is backing Leverkusen to spring an upset on home soil and pile further pressure on Villas-Boas.
"Chelsea know how important this game is and top teams are the ones who deliver under pressure," said the midfielder, who spent four years at Stamford Bridge between 2006 and 2010.
"This makes Chelsea more dangerous.
"But we can also beat them, we are playing at home after all. It is a fantastic game and everyone has been waiting for it.
"We have won both our home games and can now make it three.
"We did not get into this competition just to take part. We have the quality to advance and we need to get that into our heads."