Arsenal mess it up again

Arsenal, yet again, shot themselves in the foot in yesterdays Champions League game against Anderlecht. 3- 0 up after 58 minutes, and smiles are everywhere in the Arsenal camp - and thats the problem!
If Arsenal would have been 1-0 up at 60 mins they would have stayed focussed. Concentration would have been good, and they certainly could not, and would not have taken their foot off the pedal. As they did!
The only positives to be taken are that Arsenal will probably still qualify for the next stage of The Champions league , and in some way more importantly -they must learn the lesson from last nights game. ie In the Premier League or The Champions League you cannot drop your performance for one minute.
Arsenals weak points were highlighted yet again. With huge question marks with the defence. It will be interesting to see who Wenger signs in the next transfer window in January 2015 to attempt to improve this area of the Arsenal team.
Are Arsenal serious about really wanting to win the Champions League? or the Premier League? If so, Wenger must get the cheque book out and buy quality in key areas. Which areas and players are fairly obvious. Central defence  is not strong enough, and there are serious question marks over players such as Arteta, Monreal and Flamini.
My guess is that Wenger will buy one quality player -and that will be it. Arsenal fans will still live in hope ,yet knw deep down inside that its not enough.