With Arsenal's new signings proving to be fairly successful, a majority of Gooners everywhere mutually agree that we still need a defender. We have to do away with Squillaci and Djourou quickly. I honestly prefer a defender who has been acclimatized to the harsh unforgiving league that is the EPL. So let's hear some suggestions.

Zabaleta , Juan , Fontas , Jeffrey Bruma or Arsenal can try sign Hummels from dortmund...

Swapping Bendtner for Mexes. Rumor though.

@GunnerAFC yes i heard that too and i think it should be great.  Sagna-Koscielny-Vermaelen-Santos are probably the best choice i think, right? But with Arsenal injuries u never now.

Yeah, that line up is definitely our strongest back four. But like you said, with Arsenal injuries you never know...

Mexes would be a great back up for sure though.

HUMMELS! I have to admit we need a better replacement for puyol...he would be great for the job.

Of course we need to get rid of Squillacci, how is that he is still there? anyways i think that we need a good defender but as i don't want to see Koscielny being benched so i am thinking of Ogbonna maybe? he is quite good.

Arsenal has some good defenders I personally don't think you need to incorporate any other, just maybe a young defender but not for the starting XI. Arsenal have Metersacker and Vermalen for the central defending which are very good players, its just a matter of time for Metersacker to recover his form. as an alternative you also have Koscielny which is a descent sub. Sagna plays very well on the right and does a fair job defending and attacking but the fact he is almost 30 could be reason to find him a replacement soon. The left back side is probably the only place where arsenal could get someone new this season because Santos is not playing well and Gibbs is still young but he has not reached his full potential. 

In the end I would suggest to sign a young left and right back for less than 10million for both.
(not for starting XI) Arsenal should stay with the team they have now, give a chance to recover to Metersacker and another opportunity to shine to Gibbs, I still think he has potential. 

For a quick urgent transfer arsenal could buy Leiton Baines but i dont find it very necessary.
Bryan Obviedo is young and not worth more than 3million. He plays left back and was linked with Man. UTD some time ago.  

In my opinion, there is no need to sign high class defenders this season, just maybe some young ones with potential to become world class. 

Nathaniel Clyne and Van Der Wiel are good backup.

Gentlemen, we simply do not need anymore central defenders!
We have 3 quality CBs battling for (Verms, Kosc, & Mert) 1st choice. There is only maybe 2-3 teams that have a better line-up.
@koldimere: I think you are being very harsh on Djourou. He is a very good choice for a back-up CB. When he played terrible last year, it was mainly when he played as a fullback. He is not a FB and when he plays there we are simply giving he opposing team a handicap. However, if you watch him closely he is quite quick and has a decent tackle.
Add to these our 2 academy products: Bartley - I'm not convinced he is going to cut it but he looked ok during pre-season so I'm happy to be wrong; Miquel - I think he'll be our future CB. Unfortunately (or fortunately, however you look at it) I heard he will be loaned out to Malaga as part of the agreement for Cazorla.

In summary, I think we are set in CB. The personnel is not the problem. It is the coaching. I hope that Steve Bould addresses that this year.

As for Fullbacks, we may have some weaknesses.
RB options: Sagna is a fixture and there is no disputing he is one of the best in the world. Sadly he will be out until October-ish. Until then, it's between Jenkinson & Yennaris. Personally, I think Nico is a bright prospect and a far better defender than Jenko, despite his young age. Jenkinson plays like a winger (i.e. he bombs forward, has pace, a great cross, and likes to take on his man). Unfortunately, he is pretty terrible at defending which, strange as this may sound, is the primary job of a RB.
LB options: Gibbs is growing into his position and was looking very good at the end of last season. Unfortunately, he is made of glass. As for Santos, he seems to have the Brazilian weight-problem. But more importantly, he has the same issue as Jenkinson (i.e. he thinks he's a winger). He is not good or just too lazy to track his opposite number at times.

I agree with you footaholic. The problem is not with our CBs, it is with RB and LB. As you said gibbs and sagna are good or even very good, but their back ups are sometimes very sloppy when defending. Or just lazy.

Lastly, I come to a CDM. THIS IS WHERE WE MOST NEED TO INVEST. While we have some defenders that have some defensive attributes in their locker I think we NEED a proper CDM that is happy to sit back and be a destroyer. Someone along the lines of a Gattuso, De Rossi, Scotty Parker.
Here are our Current Midfield Options:
Cazorla, Rosicky, Ramsey, Arshavin - Attackers
Lansbury - not a CD and might not make it (although I rate him)
Wilshere, Coquelin, & Diaby - box-to-box midfielders; NOT proper CDMs
Arteta & Sahin (if he comes) - deep-lying playmaker; NOT proper CDMs
Frimpong - the ONLY proper CDM we have and he is crocked; also he is still learning his trade and is too impetuous at this stage to be a starter.

So you se we REALLY need a good defending midfielder whose only job is to break up play and pass the ball to one of our myriad attack-minded midfielders. We need someone who is close to the finished product and ready to slot right in.

My Realistic Suggestions:

These are all within a good price range (12 - 18 million Euros).
Yann M'Villa – Rennes – 21; before you ask this is NO LONGER REALISTIC (all reputable sources say it was going to happen but Wenger dropped it because he didn't like his attitude. Shame as he is also a good distributor)
Javi Garcia – Benfica - 25
Radja Naingollan – Cagliari – 23

if arsenal needs a defensive midfielder then Patrice Vieira should do the Paul Scholes and come back from retirement haha