Can Arsenal's defence stand up to its biggest week of the season?
Tensions are running high at London Colney this week, after Arsenal's weekend hammering at the hands of Liverpool raised questions over the Gunners' title ambitions. Last week there was a reported training ground row between Per Mertesacker and Yaya Sanogo, the sort that only comes to light when all is not well.
It shouldn't be forgotten that the club is in with a decent chance of silverware, they made a record signing in August, and their younger players are turning promise into worth.
Arsene Wenger's team have the second best defensive record in the Premier League, having conceded just 26 goals. At this stage last season it was 29, so at first glance the improvement doesn't seem that significant.
Of their seven defeats last term, only two came against sides that didn't finish in the top five. At the Emirates they lost to Manchester United, Chelsea and Manchester City.
This time around they've lost four times, but all of them felt meaningful; the opening-day embarrassment to Aston Villa, and then defeats at Old Trafford, the Etihad and Anfield. Once again in the biggest matches, Arsenal are struggling. Taking away their 11-goal negatives at the latter two grounds, however, the Gunners conceded a mere 15 goals in 23 games.
This year Wenger's men have won 10 home games by a 2-0 scoreline, but this week will test how far they have really come. Manchester United, Liverpool and Bayern Munich all visit in the space of eight days across three different competitions.
Wenger's Franco-German alliance
Until last weekend, Arsenal were undefeated whenever Per Mertesacker and Laurent Koscielny had played the full 90 minutes together, and no goalkeeper had more clean sheets in the league than Wojciech Szczesny's 11. The former record was blown away in dramatic style, while Petr Cech moved level with Szczesny after Chelsea's 3-0 win over Newcastle.
Before this season, the north Londoners' centre-back pairing was changing regularly due to injuries. There's an argument that captain Thomas Vermaelen is their best defender indvidually, but it's the combination of the other two's characteristics that work best.
Koscielny is a proactive defender who likes to win the ball high up the pitch. He is mobile, excellent in possession, intercepts the ball well and is good at making recovery tackles.
Mertesacker, meanwhile, is a reactive defender who prefers to drop deep because of his lack of pace. He is strong, comfortable in the air and also decent when bringing the ball out of defence.
Despite these contrasting attributes, the two still need to stay close together. It's not simply a case of allowing Koscielny to deny space between the lines and letting Mertesacker drop to the edge of his own box; the back four has to work in tandem.
Of course, this would be less of a concern if Mathieu Flamini was available to shield the centre-backs. The suspension of the holding midfielder means he will only play against Bayern.
Against Liverpool on Saturday they were facing four attackers in top form. If the defence were to push high up, then Daniel Sturridge and Raheem Sterling would use their pace to exploit the space. But if they played deeper, it would have given Luis Suarez and Philippe Coutinho room to manoeuvre. Knowing when to sit and when to sprint is the difference that marks out top full-backs - and top teams.
Wenger's quandary was obvious from the first whistle. Mertesacker gave away the foul on Suarez which led to the opening goal, while Koscielny was the nearest defender as Martin Skrtel used his thigh to score from the resulting free-kick. The second was down to Koscielny's inability to stay close to Skrtel again, but the corner came as Nacho Monreal was backing away with Sterling sprinting towards him.
Wednesday's visitors Manchester United might not be strong at present, but the Robin van Persie, Wayne Rooney and Juan Mata trio are capable of causing problems.
As Liverpool's opening two goals came from crosses, albeit set-pieces, David Moyes will likely persist with the strategy which saw his side attempt 82 against Fulham.
Pep Guardiola, meanwhile, will watch the Liverpool DVD with a wry smile on his face. He knows his forwards can be just as ruthless in front of goal, while Bayern's midfield will press their opposite numbers into relinquishing the ball.
At full-back Wenger might restore Kieran Gibbs to the starting XI after the abject performance of Monreal against Liverpool. The English youngster has been on the bench for the last month after recovering from injury.
Arsenal's full-backs like to support the attack, but it would be better for them to do so against Manchester United rather than Bayern Munich. Both teams will fancy their chances on the wings, but United will be more keen to get to the byline and put the ball into dangerous areas for the likes of former Gunner Van Persie to pounce.
The Gunners should be able to dominate the ball against Moyes' men, but few teams get the better of Guardiola's side in the possession stakes. Bayern like to use inverted-wingers and move directly towards goal, but the news that Franck Ribery will be missing is a huge blow for them. If only he had other good players to do the job, eh?