All was already lost, so of course Arsenal made an impressive start to their return leg with Bayern Munich in the Champions League round of 16 on Tuesday.

What better time, after all, to finally display a little bit of good form than when you’re already losing 5-1 from a first-leg hammering three weeks earlier. To the Londoners and their embattled manager Arsene Wenger, it’s just a shame that it only lasted for a half. And that whereas the Gunners got just one goal in this superior half, Bayern got five more in theirs.

[ Follow FC Yahoo on social media: Twitter | Facebook | Tumblr ]

That’s right, Arsenal lost 5-1 to Bayern again. At home. And, yes, your math is correct. That made it a 10-2 aggregate win for Bayern, which strolled into the quarterfinals with improbable ease.

A second destruction by the German juggernauts of the water-treading Gunners will further amp up pressure for the club to part with Wenger, whose contract expires in the summer but who has reportedly been offered a new deal to extend his two-decade stay. Arsenal has now lost five of its last seven games and has failed to survive the round of 16 of the Champions League for seven straight years. It has also, of course, been a dozen seasons since Arsenal last won the Premier League, and it surely won’t this year either, lagging leader Chelsea by 16 points.

But, in the first half, Wenger’s team didn’t look bad at all. Far from it.

Just 11 minutes in, Theo Walcott was through, but his touch was imperfect as goalkeeper Manuel Neuer beat him to the ball. Three minutes later, Olivier Giroud nodded a header off the outside of the post.

In the 20th minute, Arsenal took a lead. Walcott dribbled in from the flank and tried to play in Giroud, but the ball came back to him off the Frenchman’s ankles. Walcott pushed on and blasted the ball into the roof of the goal, where Manuel Neuer couldn’t get to it.

After the half hour, Walcott would have two more opportunities. First, his very reasonable shout for a penalty from a Xabi Alonso challenge was denied.

Then, he had the same sort of look as on his goal. Only from a tighter angle, with a few teammates along with him who were better positioned. But he opted for the hard shot yet again, which was off target.

After halftime, everything changed rather dramatically.

First, Laurent Koscielny was sent off. He was initially given a yellow for taking down Robert Lewandowski in the Arsenal box. But after input from the goal-line referee, it was changed to a red.

Lewandowski converted his own penalty.

Then, in a 17-minute span from the 68th to the 85th minutes, Arsenal would give up four more.

The first was courtesy of a few woeful mistakes in the back by Arsenal. Alexis Sanchez ultimately gifted Arjen Robben a free run at goal. The Dutchman made no mistake.

Then, Douglas Costa was launched from another bad Arsenal turnover with much of the team committed high up the field. The zippy Brazilian had almost literally half the field to himself. He kept on running, ignored his wide-open teammates and deposited his shot behind David Ospina. 3-1.

On yet another Gunner giveaway in their own half, Arturo Vidal scooped Ospina for a fourth.

And Renato Sanches was given the time and space to deliver a preposterously simple ball through to Douglas Costa, who handed Vidal a tap-in. 5-1.

The whole thing was so embarrassing that late on, Sanchez – one of the few real Arsenal superstars who has apparently fallen out with Wenger and is said to be angling for a departure this summer – was seen laughing to goalkeeper Petr Cech on the bench.

The ever more helpless-sounding Wenger managed to somehow blame a double-digit destruction on the referee’s decision to send off Koscielny after the game.

Certainly, it didn’t help that Arsenal lost its best defender. But that was hardly all that was amiss.

Perhaps Alexis had it right. For Arsenal’s second-half display, just as three weeks ago, was laughable.

Leander Schaerlaeckens is a soccer columnist for Yahoo Sports. Follow him on Twitter @LeanderAlphabet.