Two defeats in three league matches have cut short Carlo Ancelotti's honeymoon period as Chelsea coach but his concerns pale into insignificance alongside those of Atletico Madrid counterpart Abel Resino.
Saturday's 2-1 reverse at Aston Villa left Chelsea trailing Manchester United by one point at the top of the Premier League and captain John Terry stamping his feet in disapproval as the second Villa goal went in.
It hardly represented a crisis, however, and victory over Atletico at Stamford Bridge on Wednesday will virtually assure Chelsea a place in the knockout round of this season's Champions League.
Resino's Atletico though are having a torrid time and a game at Chelsea, who are unbeaten in 19 home Champions League ties, is hardly the easiest task to try and reverse the slump.
Sunday's 3-0 defeat by Osasuna was their third defeat in seven league games and they are a distant 15th in La Liga.
"The football gods are being very unfair to us," Resino told reporters on Sunday. "We had a lot of chances but that's what happens when you are on a bad run, the ball just won't go in the net."
Defeat by Porto in their last Champions League outing also left Atletico at the bottom of Group D with one point. If they suffer another reverse in London their hopes of progressing will be fading fast.
Brazilian midfielder Cleber Santana says the Chelsea clash is coming at a key moment for the club as they seek to turn their faltering season around.
"We are facing a very difficult encounter and we have to be at the top of our game," he said. "It's a vital match for us."
Atletico will have Diego Forlan back after the Uruguay striker missed the Osasuna defeat because of fatigue and a muscle problem following his midweek international exploits.
Chelsea will again be without Didier Drogba, who is completing his European ban for his behaviour in the semi-final defeat by Barcelona last season.
The loss of the Ivory Coast striker has been negated by the form of Nicolas Anelka who has scored in both of Chelsea's Champions League victories this season.
Chelsea: 1-Petr Cech; 2-Branislav Ivanovic, 6-Ricardo Carvalho, 26-John Terry, 3-Ashley Cole; 21-Salomon Kalou, 5-Michael Essien, 13-Michael Ballack, 8-Frank Lampard, 15-Florent Malouda; 39-Nicolas Anelka.
Atletico Madrid: 1-Sergio Asenjo; 17-Tomas Ujfalusi, 22-Pablo Ibanez, 16-Juanito, 21-Luis Perea; 11-Maxi Rodriguez, 9-Jurado, 12-Paulo Assuncao, 23-Cleber Santana, 20-Simao Sabrosa; 7-Diego Forlan.
(additional reporting by Iain Rogers, editing by Tony Jimenez)