Arsenal manager Arsene Wenger, who admitted he didn't recognise the team which slumped to defeat to West Bromwich Albion at the weekend, faces a crucial week which could define his side's season.
The Gunners' Premier League aspirations will be under the microscope at Stamford Bridge on Sunday when they take on Chelsea. But Tuesday sees a test of their backbone as well as their style in a tricky UEFA Champions League trip to Partizan Belgrade.
The Serbian side, playing in Europe's elite event for the first time in seven years, have never won a home tie in the competition, but will have taken heart from the way that unheralded West Brom picked their way through a sleepy Arsenal backline in the 3-2 win on Saturday.
Wenger has little time to solve the mystery of that Emirates fiasco. "I didn't recognise my team and we have to sit down together to analyse what happened," said the coach. "Something was not right. It's unusual to see a team as flat as we were."
Goalkeeper Manuel Almunia was widely condemned for another poor performance and Wenger, who courted Fulham's Australian goalkeeper Mark Schwarzer in the summer, is believed to be lining up a bid for Liverpool's Pepe Reina once the transfer window reopens. But that is not until January.
Almunia has been ruled out of Tuesday's game with an elbow injury and will be replaced by Lukasz Fabianski. Wenger insisted on Monday he would have played Almunia if the keeper had been fit.
"We have Manual Almunia out," Wenger said. "He has a problem with his elbow. He caught it when he made the penalty on Saturday." The French boss added: "(The goalkeeper) is always the easy target, the easy scapegoat. But we win together and we lose together even if people think he made a mistake on the second goal."
Wenger continued: "For Fabianski, it is another big chance - but you want a goalkeeper or any player to grab the chance when you get it. As a manager you can give a chance to a player who is good enough and I believe in his talent.
"He gets another opportunity to show how good he is. I want him to show how good he is. There is only one way to show confidence in a player and that is to put him on the pitch and give him his chance."
Arsenal won their opening UEFA Champions League game 6-0 against Braga on the same night that Partizan lost 1-0 at Shakhtar Donetsk. But the Gunners' away record in Europe doesn't make comfortable reading for Wenger with his team having lost their last three away games - 4-1 at Barcelona in last season's quarter-final, 2-1 at Porto in the round of 16 and 1-0 at Olympiacos in the the group stages.
They have only won two of their last 10 away matches in the competition. When Partizan last appeared in the UEFA Champions League in 2003/04, they failed to win at home in five attempts, including two qualifying rounds. But a defeat to Newcastle was their only loss, the other four games all ending in draws.
This season, they saw off FC Pyunik and HJK Helsinki in the qualifying rounds before defeating Anderlecht 3-2 in a penalty shoot-out win after two play-off games each finished 2-2.
Brazilian striker Cleo scored three goals over the tie, including two in the away leg. The Serbian champions will also be looking to experienced midfielder Sasa Ilic for influence in tomorrow's game, who they hope will be able to dominate proceedings amongst an understrength and injury-ravaged Arsenal midfield.
Wenger added: "What I expect is for Partizan to play a highly passionate game and to try to catch us on the break. They have the traditional strengths of Serbian teams - they are intelligent, with a good technique and in the final third, if you give them room they are always dangerous."