Carling Cup hangover? Or a grossly complacent and sloppy performance by a group of players that thought they only had to turn up to win? Seeing as Arsene Wenger made eight changes from the team that started against Spurs midweek, let's go with the latter, shall we?

Before talking about Arsenal’s display, it is only fair to say that West Brom were magnificent yesterday and thoroughly deserved their victory. They competed from the first whistle to the last. They took their game to the Gunners and looked the better side all afternoon. They attacked with pace and real intent and were organised and focussed in defence.

Arsene Wenger Put His Head in His Hands at The Grove Yesterday - He Wasn't The Only One ©Getty Images

However, as good as West Brom were, it does not excuse the performance of an Arsenal team that has aspirations of winning a title. It was lamentable, undisciplined and totally unprofessional. It would be nice to put it down the team having a collective “off-day” but, unfortunately, one couldn’t help but sense that most of yesterday’s performance was down to arrogance and laziness.

Abou Diaby and Alex Song seemed to be having their own private competition as to who could give the ball away the most with artistic impression points being added for doing so in the slackest way possible. Andrey Arshavin looked disinterested, which is becoming something of a trademark for him, and you might have thought that Emmanuel Eboue, given a Premier League start in a season where he is more likely to play as a utility player, might have been keen to impress. You would have thought wrong.

And that was just the midfield. Up front, Marouane Chamakh was totally anonymous and to say the defence looked shaky all afternoon would be far too generous. The fullbacks were constantly terrorised by West Brom’s wide-players and, at times, the back four looked all over the place.

And then there was the goalkeeping. It was hard to know whether to actually feel a little sorry for Manuel Almunia. In the first half he kept the Gunners in the game making one tremendous save and also saving a penalty. After the break though, a catastrophic blunder saw him throw in the Baggies’s second goal and all his good work was undone. Any sympathy you might feel soon gets lost in the frustration of seeing Arsenal’s goalkeeper yet again take one step forward and two steps back. In an afternoon of ineptitude, it was his mistake that essentially cost Arsenal the match - but he wasn't solely to blame for what was a humiliating defeat.

One also has to question Arsene Wenger. Having got to the interval at nil-nil - and to have been fortunate to have done so - you might have thought this would have been one of the rare occasions when the Frenchman had a tea-throwing tantrum in the dressing room at half-time. And if that didn’t happen, surely he would deliver an inspirational speech that would pull the players out of their malaise and onto glory? Whatever he said at the interval, it had zero impact because the second half started as shoddily as the first half had been played out - only this time West Brom punished the Gunners with two quick and well-deserved goals.

Finally, Wenger saw fit to replace the pathetic Diaby and hapless Eboue with Tomas Rosicky and Jack Wilshere. It was a change that might have been better at half-time and before conceding a two-goal lead, but better late than never. Wilshere’s first contribution was to sweep a gorgeous ball out to the left-wing. It was a pass that showed more maturity, class and vision than anything Abou Diaby had produced in the preceding hour.

Though the Gunners conceded a third on the break amid more shambolic defending, the introductions of the substitutes did improve matters greatly and Samir Nasri, the one player in the starting eleven who could still hold his head up high at the final whistle, profited from the impetus that the fresh blood provided, scoring a couple in reply. As it was, the fight-back came too late and, to be honest, anything other than a West Brom win would have been a travesty of an outcome based on the whole ninety minutes. Arsenal got exactly what they deserved - absolutely nothing.

Arsene Wenger said after the match they he would have to analyse what went wrong but that suggests there was some sort of mystery as to why the Gunners were so poor. I don’t think there was any mystery to it at all and several individuals in that squad need to take a good look at themselves and ask themselves a few searching questions. The manager should at least be a bit clearer in his mind as to who the passengers are in his squad and who the real winners are.

The only consolation on the back of yesterday’s shambles was that, over the weekend, Chelsea and Spurs were also beaten and Manchester United and Liverpool were held to draws. Whilst it is infuriating to have squandered a golden opportunity to have made up some ground on Chelsea ahead of next weekend’s trip to Stamford Bridge, the other results did offer a bit of damage limitation.

It was all such a contrast to the glorious midweek trip to Spurs in the Carling Cup. That night Arsenal played some scintillating football and came away with a rousing and thoroughly-deserved win. It was a marvellous collective effort but Jack Wilshere does have to be singled out for particular praise. He orchestrated more or less everything good that Arsenal did and the whole game marched to his beat.

The kid is eighteen years old and yet he has the vision, temperament and bravery of a player ten years older than that. It would be easy to get carried away with that one performance but when he came on yesterday he looked far more accomplished and comfortable on the ball than either Diaby and Song. Tuesday night was not a flash in the pan for Jack Wilshere. He has looked good all season and, having been presented with a chance by Arsene Wenger, he appears to be taking it. We are going to see a lot more from him in the coming months.

The players now have to pick themselves up ahead of Tuesday night’s trip to Partizan Belgrade in the Champions League. Hopefully, their embarrassment at yesterday’s display ought to be motivation enough to turn things around - and they certainly need to ensure they do that ahead of next weekend.