Bayern Munich 5 Arsenal 1: Six things we learned as Arsene Wenger's side are blown away by Bavarian giants

Laurent Koscielny's injury sparks Arsenal collapse as Bayern's ageing stars take giant step to Champions League quarter-finals

Arjen Robben was at the heart of everything Bayern did well on Wednesday night (Getty)

Bayern Munich's ageing stars rolled back the years in a 5-1 victory that leaves Arsenal with no hope of making it through this Champions League tie.

The hosts dominated from the off, but it was a Laurent Koscielny injury in the second-half that sparked Arsenal's collapse.

Arjen Robben and Philipp Lahm created several chances early on and it was the Dutchman who opened the scoring with a trademark goal on 11 minutes.

He cut in on from the right, and walloped one into the far left corner, leaving David Ospina no chance in the Arsenal goal.

The hosts looked like they could run away with it from there but, against the run of play Arsenal got a penalty on the half hour mark after Robert Lewandowski's foul on Laurent Koscielny.

​While the referee's decision was harsh on Lewandowski, Arsenal knew they had to make the most of it, and they did - just.

Alexis Sanchez's poor effort was saved by Manuel Neuer who parried it back into the Chilean's path. Sanchez fluffed the rebound but was lucky enough to get a third chance and made no mistake that time, passing the ball into the Bayern net under pressure from three defenders.

But it started to go wrong in the second-half with that injury to captain Koscielny. Shortly after Gabriel came on in his place, Bayern scored two in three minutes.

First Lewandowski scored a wonderful header and then his deft flick between the legs put Thiago Alcantara - who was excellent on the night - in for a third.

Thiago scored again seven minutes later through a deflected shot from the edge of the box before Thomas Muller put the icing on the cake.

It will be more a case of damage limitation for Arsenal when the side's meet again in north London.

Here are six things we learned on the night...

1. Arsene Wenger has some serious questions to ask about his future

Does Arsene Wenger have the motivation to carry on? (Bongarts/Getty Images)

Another season, another European disappointment for Arsenal. With the club's Premier League hopes already gone, Arsene Wenger must ask himself if he really has the motivation to carry on.

Arsenal were crushed tonight. Outplayed, outfought and outrun. Calls for his resignation were already growing and that performance is sure to see them increase.

For a club of such stature, Arsenal have gone far too long without challenging for major honours.

Will tonight's humbling be the final straw for Arsene?

2. Bayern are serious Champions League contenders

Carlo Ancelotti has a formidable record in this competition (AFP/Getty Images)

There may have been doubts over this ageing Bayern team coming into tonight but their second-half performance proved they are still among the very best in Europe.

Carlo Ancelotti has won this competition three times before and while there have been some signs of unrest in Bavaria, it would be a brave person who bets against him getting a fourth.

Bayern are seven points clear in the Bundesliga despite not playing as well as in recent seasons. If they can wrap that up early again, they can focus all their efforts on this competition.

3. Arsene Wenger’s faith in David Ospina is questionable

David Ospina has started all seven of Arsenal's Champions League game's this season (Arsenal FC via Getty Images)

It was a nervy start for the Colombian whose first touch was a scuffed kick along the floor that nearly saw Bayern in on goal.

Despite making some eye-catching saves there's no way Arsenal's defence can be inspired when they look back and see Ospina rather than the more assured Petr Cech between the sticks.

While Wenger insists he has two world class keepers in his squad, it seems increasingly strange that he doesn't stick with his number one for Europe's biggest club competition.

4. Alex Oxlade-Chamberlain should play more often

Oxlade-Chamberlain's biggest weakness is being too versatile (AFP/Getty Images)

In this game and against Hull the young England international has shown he has more than enough quality to hold down a regular place in the Arsenal team.

Always a willing runner and always assured on the ball, Oxlade-Chamberlain offers a more direct approach than his teammates.

As well as setting up several chances going forward, the 23-year-old also acted as the first line of defence, constantly chasing down his opponents.

His biggest weakness has perhaps been summed up by these last two games - no one quite knows what his best position is.

​5. Bayern’s ageing stars have still got it

Xabi Alonso pulled the strings in midfield (Bongarts/Getty Images)

Arjen Robben and Philipp Lahm provided a masterclass of wing and full-back play down the right flank - scoring one and creating another - while Xabi Alonso pulled the strings in midfield.

Those three may have a combined age of 101 years, but they proved they can still mix it with the best in Europe.

Bayern's biggest problem will be replacing them. Robben insists he's happy to go on for another few years but Lahm and Alonso will both be retiring at the end of the season. The end of an era beckons - but not quite yet.

6. Arsenal have problems at left-back

Gibbs had a torrid time against Arjen Robben (Arsenal FC via Getty Images)

Neither Kieran Gibbs nor Nacho Monreal have managed to nail down a starting place for Arsenal over the past few years.

Gibbs got the nod tonight and had a torrid start against Arjen Robben and Philipp Lahm. Robben has been among the world's very best in that position in the past decade and Gibbs was simply no match.

If Arsenal want to mix it with the best in Europe, this is surely an area Arsene Wenger will need to strengthen in the summer.