It is rare that a month goes by without somebody emailing me or tweeting me to point out that John Giles has said on television that it's not the formation that matters but the players. Many seem to offer the line aggressively, as though the assertion somehow invalidates the notion of tactics in football.

To draw that conclusion, though, is to misunderstand what tactics and formations are, to fall into the trap of thinking that players can somehow be separated from the tactical framework. Nobody ever played a game of football without both players and tactics. It's simply not possible: as soon as there is more than one player, there is necessarily a relationship between them and, however little thought goes into that, that is tactical. But that doesn't mean, as some appear to think, that the formation outweighs the players whose distribution it describes.

Giles is far from the only figure who has tried to wrest the discussion away from formations towards players. Slaven Bilic, when he was coach of Croatia, tended to deflect tactical questions by insisting that modern football was becoming less and less about formations and more and more about the attributes of players. That didn't mean, though, that he thought tactics unimportant: rather that, for him, setting up a team was less about setting up a template and fitting players into it than trying to assemble a series of attributes – the players – in the most effective distribution for the circumstances.

His side would probably be described as a 4-1-3-2, but that was far from the whole story. The two centre-backs, Robert Kovac and Josip Simunic, provided the basic platform. The right-back, Vedran Corluka, was relatively defensive, capable of tucking in and becoming an auxiliary centre-back if necessary, which had two effects. One was to free the left-back, Danijel Pranjic, to attack, overlapping Niko Kranjcar, who would naturally cut inside from a left-sided attacking midfield role. The other was to allow the tireless Darijo Srna to patrol the whole of the right flank, getting forward to provide width, but covering back and even sliding into the centre if need-be to provide additional cover alongside Niko Kovac.

Kovac, a player of profound tactical intelligence, was the hub of the side, sitting in front of the two centre-backs and essentially filling holes, his reading of the game allowing Bilic to field what was effectively a front five (or four-and-a-half, given Srna's energy and willingness to shuttle back). Kranjcar, on the left, had limited defensive responsibility, while Luka Modric could operate almost as an old-fashioned No10, haunting the final third, popping up wherever there was space. On top of that creativity, Croatia could also field a front two – Eduardo, whose guile and finishing were complemented perfectly by the energy and raw physicality of Ivica Olic.

4-1-3-2 was only ever a rough notation. Stop the action at any moment and it could appear as a 3-2-3-1-1, or a 3-1-5-1, or a 5-1-2-2, but that doesn't mean it was wrong to describe the shape as 4-1-3-2: rather that was the best of the crude terms we commonly use to give a general indication of the shape. Offering the formation rarely gives anything like the full story of how a team plays.

As another example, take Manchester City, who on Wednesday night, in their 2-1 victory over CSKA Moscow, played as they have for much of this season, in what is probably best described as a 4-4-2. The back four was relatively straightforward. Fernandinho and Yaya Touré sat deep in central midfield: both have the capacity to spring forwards, although Touré has more licence. Jesus Navas played wide on the right, his pace allowing him to cover almost the entirety of the flank: his heat map extended from the edge of his own box to the CSKA goalline.

On the left, David Silva was tucked in and had a range of movement that was more lateral and less longitudinal than Navas's, allowing Aleksandar Kolarov to overlap (Gaël Clichy may be a better defender than the Serbian, but Silva's tendency to drift infield means he is a more natural tactical fit with him than Clichy).

Sergio Agüero then functioned as a second striker, just off Alvaro Negredo, although not so deep that he could be considered an attacking midfielder. The difference between the two systems is often slight (arbitrary even), but this was pretty clearly 4-4-2 – albeit one quite different from the blockish 4-4-2s that prevailed in Britain in the late 80s, or the rigid lines of the 4-4-2 of Arrigo Sacchi's Milan.

Many blamed City's defeat to Bayern Munich – or at least the comprehensive nature of that defeat – on the fact they played a 4-4-2, but that is shorthand for a more complex truth. Largely, of course, Bayern won because they moved the ball with astonishing speed and precision, but City would probably have had a better chance of stopping them with more defensive strength in central midfield: with Agüero playing so high, with neither central midfielder a true holder (at Shakhtar, Fernandinho would occupy what is now the Touré role alongside a more defensively minded player, either Tomas Hubschman or Taras Stepanenko) and with both wide players having largely creative briefs, City were overwhelmed.

The 4-4-2 was part of the issue, but had they played with more defensive players in central midfield, or with wide players who tucked in and sat deep (as, say, Roy Hodgson's Fulham often did in Europe, or as Gerard Houllier's Liverpool did away to Roma in the Uefa Cup in 2001 – a game discussed in detail in The Anatomy of Liverpool), they might have posed more awkward opposition.

There are trends in football away from certain shapes and towards certain others. When certain formations face off, the stress points are usually fairly predictable (for instance, if Team A plays 4-4-2 and Team B plays 4-3-3, then the likelihood is that B will dominate possession because it should control the centre by dint of its additional central midfielder, but A should pose a greater threat from wide areas). But these are generalities, rules of thumb, useful guides, but no more.

What formation a team is playing, anyway, is often in the eye of the beholder . How deep does the second striker have to be for 4-4-2 to become 4-4-1-1? How advanced do the wide players have to be for that to become 4-2-3-1? Besides which, individual players will interpret different roles differently: Lionel Messi and James Milner have both played on the right of 4-2-3-1s, but they did it very differently.

The designations we give formations are useful starting point, but that's all. They give a general idea of the structure of a team and a game and of the relationships of players to each other, but the game itself is decided by the interaction of those bundles of attributes.