Schalke 04 must produce a big performance if they want to live with Jose Mourinho's Chelsea on Tuesday in the Champions League, the German's boss Horst Heldt has insisted.
Schalke face back-to-back clashes in Europe against Chelsea as Tuesday's match at Gelsenkirchen's Veltins Arena will be followed by a trip to Stamford Bridge on November 6.
Having won both of their Group E matches against Steaua Bucharest and FC Basel, leaders Schalke face a big test of their mettle against second-placed Chelsea.
The Blues crashed to a shock 2-1 defeat to Swiss champions Basel at Stamford Bridge in their opening match, but Schalke have suffered from erratic form this season.
Having laboured to a 3-2 win at Bundesliga bottom side Eintracht Braunschweig on Saturday, Schalke twice came from behind before Roman Neustaedter's 91st-minute winner.
"If we want to survive against Chelsea, we desperately need an improvement in individual performances," fumed director of sport Heldt.
The Blues' boss rates 2012 Champions League-title winners Chelsea as "top favourites for the title" and insisted Schalke need a "much better performance than in Braunschweig".
Schalke are hoping to welcome back goalkeeper Timo Hildebrand from a back injury, while US midfielder Jermaine Jones and Ghana star Kevin-Prince Boateng should be fit after knee injuries.
But Schalke look to be without defensive midfielder Marco Hoeger, who twisted his knee against Braunschweig.
Chelsea badly need a win in Gelsenkirchen to build on their 4-0 win at Steaua Bucharest as they bounced back from their Basel defeat.
"It's an important game for us," said Chelsea goalkeeper Petr Cech.
"We dropped three points against Basel at home, but we recovered that at (Steaua) Bucharest and now we play two games with Schalke and we have to make sure we get points to help us qualify, but it will be a tough test.
"With two wins, it's always better."
Chelsea, who are second in the Premier League, enjoyed a 4-1 win at home to Cardiff City on Saturday as they bounced back with goals by Samuel Eto'o, Brazil's Oscar and Eden Hazard after the Welsh side poached an early lead.
Blues boss Mourinho was sent to the stands for the last 20 minutes after protesting about Cardiff's time-wasting tactics in the second half.
Chelsea are unbeaten in their last six games since their shock defeat at home to Basel in the Champions League and have scored 10 goals in their last three games.
Ashley Cole is likely to miss the match in Gelsenkirchen after suffering a rib injury with Ryan Bertrand having deputised for him against Cardiff.
Germany winger Andre Schuerrle, who missed the Cardiff game with a thigh injury, could return.
Spain striker Fernando Torres is in contention after returning from a knee injury and made a substitute appearance against Cardiff, while Mourinho must choose between him, Eto'o and Demba Ba to lead the line.