When Arsene Wenger took over at Arsenal, some 18 years ago, he inherited a 3-5-2 system from Bruce Rioch. Keown, Adams and Bould formed a triumvirate at centre half with Lee Dixon and Nigel Winterburn deployed as nominal wing backs. Considering all five of those defenders were either in or on the cusp of their 30s at the time, it obviously was not a sustainable system in the long term given the energy and pace required to make the formation work. That Wenger has never returned to it since switching to a kind of 4-4-2 / 4-3-1-2 in the summer of 1997 suggests the manager is not a fan.

Wenger puts a lot of emphasis on his full backs. In that respect, he admits to taking influence from the Brazilian side of the 1970s and their use of the lateral style full back. (After a buccaneering display against Aston Villa in 2006, Wenger gushed that Emmanuel Eboue played ¨like Garrincha,¨ who wasn´t even a lateral.) Wenger has generally chosen to balance his full backs. To distill it in as dejargonated a manner as possible, he likes one ´winger style´ full back, usually his left back, and one who is more of a pure defender. Essentially, one of his full backs behaves more like a third centre half and the other more like a winger.

In most of Wenger's Arsenal sides, the thrust has come from the left. Ashley Cole, Gael Clichy and Kieran Gibbs were all wingers during their formative years whilst Silvinho and Andre Santos were very much full backs in their native 'lateral' mould. This is usually helpful because Arsenal's left sided midfielders tend to have a license to drift in field and make play, like Robert Pires, Andrey Arshavin and Santi Cazorla. Meanwhile, Overmars tended to tuck in but much higher up the pitch as a kind of wide striker to feed off of Dennis Bergkamp's laser guided through balls. Effectively, Arsenal's left back is relied upon to provide width to Arsenal's attacks.

The right back tends to be a more secure presence alongside the centre halves. Think Sagna and Lauren. Lee Dixon survived under Arsene Wenger for slightly longer than Nigel Winterburn for this reason, legs were more important on Winterburn's flank, for Dixon, his brain meant he could fulfill the more conservative expectations of the right back for a couple of seasons longer. Wenger was convinced to buy Bacary Sagna in the summer of 2007 much to the surprise of many. With Emmanuel Eboue and Justin Hoyte as options, many did not consider right back to be a priority position. However, both Eboue and left back Clichy took on the roving full back duty and Wenger wanted to reintroduce this sense of balance to his team. Justin Hoyte was a centre half as well as a right back, but the manager clearly did not have faith in him to hold down the position in the long term.

Mathieu Debuchy was considered a logical replacement for Bacary Sagna because he shares many of his compatriot's defensive attributes. He is strong in the air and covers his back post well when the ball is whipped in from the left. It is telling that both Nacho Monreal and Mathieu Debuchy have been entrusted with the centre half position during this campaign. Monreal is a more conservative alternative to Gibbs. He plays close to his centre backs but is not quite as penetrative going forward, which explains the manager's preference for Gibbs ahead of the Spaniard. However, in the long term, there is potentially an interesting development in the right back position.

Both Hector Bellerin and Carl Jenkinson fit the requirements for the more penetrative full back position. Even if, at 29 years old, you accept that Mathieu Debuchy is a relatively short term solution there, it is still unlikely that both Jenkinson and Bellerin will ever co-exist in the Arsenal squad. Both Bellerin and Jenkinson boast excellent delivery from the right hand side. Jenkinson can swing a teasing cross for a striker´s bonce with the best of them. Something that struck me about Bellerin in the U-21s was the variety in his delivery and you have already seen this exemplified in his sporadic first team appearances.

Bellerin started out as a midfielder in Barcelona's famous La Masia academy and is therefore technically more adept than Jenkinson. He knows how to use combination play to get closer to the by line. He chooses the right method of delivery too. If the ball needs standing up to the back post (Giroud v Stoke) he´ll do so, if it needs to be whipped, whacked or stroked into the area, he tends to find the right technique. During the second half against Newcastle, he tried a beautifully angled cut back for Giroud, which he hit along the floor with his laces. Had Mike Williamson not stretched out a limb to intercept, it would have been a quite wonderfully weighted pass into Giroud's stride. That said, Jenkinson is physically more robust than Bellerin, who can struggle with a more physical examination, as we saw against Stoke. If Bellerin is a paintbrush, then Jenkinson is a jackhammer.

Once the Darwinist grapple between the two is settled, another task awaits the victor. They will not just have to duke it out with an established right back, they will have to compete with Kieran Gibbs too. At the moment, Gibbs is the full back expected to provide the thrust. Either Bellerin or Jenkinson will have to convince Arsene Wenger that they provide more of an attacking threat than Kieran Gibbs. It is hard to envisage Jenkerin (or Bellinson) playing in the same side as Kieran Gibbs on a regular basis because it would lack balance and give Arsenal's defensive midfielder quite the workload. On Saturday, we got more of a glimpse of the real Hector Bellerin, after tough assignments away from home against Dortmund and Stoke, but this only represents the beginning of his battle at Arsenal. LD.