Southampton's shock win over Arsenal was, weirdly, one of the more predictable upsets you can get.

Arsenal given the chance to go top of the table and take control of the title race just meant everyone expected them to fall at the simplest of hurdles.

Saints have been in the worst of form recently, but they still managed to concede several times to Koeman's men, who had picked a team with the aim of stopping the Gunners.

Mane and Long's brilliance is one thing, but the Arsenal defence opened up their old wounds with some shambolic defending that was a throwback to the days of Pascal Cygan or Sebastian Squillaci.

We almost felt sorry for Petr Cech at times this evening, as his defence almost invited the runs of Shane Long on to them and Flamini failed to screen the defence at all, again.

Here are FIVE things we learnt tonight..

Arsenal need Alexis

The Gunners have succeeded without Alexis of late, but, his ability to get a goal out of nothing was sorely missed against Southampton.

Walcott is a nice option to have, but he cannot be compared to the world class talent of Alexis Sanchez. The Chilean is, along with Aaron Ramsey, the player that Arsenal miss the most.

Saints stayed off the turkey

Southampton looked so much sharper than Arsenal its hard to know whether it was fatigue or less turkey. The Saints have a good record on Boxing Day and this was an utterly priceless victory for the Saints.

Koeman clearly has his side well drilled and he masterminded the perfect performance.

Shane Long is a valuable plan B

Long, aside from tripping up Koscielny, was utterly brilliant this evening.

The Irishman's work-rate has always been one of his best attributes and he utterly harassed both Per Mertesacker and Laurent Koscielny throughout the game at St Mary's.

The ex-Hull man has been criticised for his goal scoring record in the past, but he proved that he is a great second choice to Pelle when the Saints want to play a brand of fast breaking football. The partnership of Long and Mane will strike fear into many a defence.

Gunners still misfire

Whenever it looks like Arsenal will finally mount a proper challenge, they manage to show us all that they have never really fixed their deep-lying issues.

Arsenal's lack of a classy defensive midfielder and shaky defence cost them once again here and they failed to produce a performance when it was most needed. Mesut Ozil has disappeared when he was most needed and you wonder who will really stand up for Arsenal when pushing for victory.

Ozil will never be reliable

The nature of flair players means they are often incredibly inconsistent. The problem with someone as high profile as Mesut Ozil, is that each quiet game looks to be a glaringly poor performance.

A man of such class rightfully gets a lot of defensive attention from the opposition, but the Gunners should not solely place their faith in Ozil if they are going to challenge for the biggest trophies.