Antonio Valencia is receiving a lot of praise for his forty-minute spell as an emergency right back against Chelsea on Wednesday night.

The Ecuadorean was perhaps not the expected choice to fill in for the injured Rafael, with Park Ji-Sung’s famed energy levels and tenacity probably making him a more obvious candidate at the time.

However, Sir Alex Ferguson had decided to let a winger do a full back’s job only four days earlier against West Ham, when Ryan Giggs played at left back for the second half in place of Patrice Evra. The tactical switch worked very well on that occasion, and the results were just as satisfying at Stamford Bridge too.

If United’s back four has looked experimental at times lately then that is entirely understandable. Due to injury and suspension, defensive resources have been stretched. John O’Shea and Wes Brown both have vast experience at right back but were unavailable on Wednesday night; it was telling, too, that the beleaguered Jonny Evans, who has spent some time at full back, was overlooked from the bench when the need arose to replace Rafael.

Evans, of course, was sent off against Bolton in March, his last appearance for the first team, and his dismissal resulted in a defensive reshuffle then, with Michael Carrick moving to central defence for the last portion of the match.

While necessity has been the mother of invention, then, in terms of the recent successful deployment of Giggs and now Valencia at full back, it’s also worth remembering the recent FA Cup tie against Arsenal that saw Rafael and Fabio line up as wingers. The personnel United have used in wide areas has been particularly interesting for several weeks now. In fact, it reminds me of an article that Jonathan Wilson, the Guardian’s resident tactical expert, wrote for the newspaper’s website last October.

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Wilson’s topic was Barcelona’s full backs and how far they push up the pitch. His theory was that, with the forward pressing of Dani Alves, in particular, being both a primary source of attacking width and also an effective way of countering teams that sit deep, the Spanish side’s formation was morphing into a curious throwback to a system supposedly consigned to history. With Vittorio Pozzo in charge, Italy’s two World Cup wins in 1934 and 1938 were achieved with what was known as the W-W formation, essentially a 2-3-2-3. With the two wide defenders playing higher up the pitch than where modern full backs would traditionally operate, alongside a deep-lying midfielder they would form a floating trio in front of the centre backs. The deep-lying midfielder was the hub of the team, dropping almost into defence to receive the ball as the full backs pushed on.

This might all sound a bit theoretical. It makes more sense when players’ names are added to the equation. In Barcelona’s case, as Wilson explained, the deep-lying midfielder who practically becomes another centre-half is Sergio Busquets. For United, the equivalent player would be Michael Carrick. Given his vastly improved performance on Wednesday night – his best for two seasons at least – it is particularly exciting to consider the possibility of a prolonged return to form for the United midfielder alongside the potential shown by two of our wingers at full back recently.

Giggs and Valencia are clearly not long-term options in wide defensive positions, but Patrice Evra was bought with a reputation as a left-sided defender who could also play on the wing and nobody would doubt Rafael’s willingness to go forward either. If United’s regular full backs were encouraged to attack even more than they already do then Michael Carrick, with some experience in defence himself, would be the ideal covering midfielder in, potentially, our very own W-W.

You can follow William Abbs on Twitter @WilliamAbbs

Read more of Willam's articles at the excellent 'Red Flag Flying High'

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