What if Pietersen had played for England this summer?

We were regularly invited, throughout the dark period when England lost seven Tests out of nine earlier this year, to imagine a better, happier world: an England team with Kevin Pietersen in it. Well, let's imagine it. Not flippantly or sarcastically but thoughtfully, as a historian would approach a legitimate "what if?" or "counter-factual". A real historian would calculate the cost - or benefit - of KP's absence methodically rather than emotionally; he would be guided by evidence rather than personality; and though he would necessarily have to make assumptions and projections, our historian would acknowledge where facts ended and where informed predictions began.

First, who would Pietersen have played instead of? In his final Test, in Sydney in January this year, Pietersen played as one of three middle-order batsmen: Ian Bell and Gary Ballance being the other two (Joe Root was left out). Changing the side's structure to create an extra middle-order batting spot was extremely unlikely: the selectors knew that in the absence of a genuine spin alternative, Moeen Ali had to bat at six as the spinning allrounder.

This left space for only five batsmen, two of them openers. So, coming into the two home series against Sri Lanka and India, England had four players vying for three middle-order spots: Pietersen, Bell, Ballance and Root. From a purely cricketing perspective, who should they pick?

As the most complete and technically accomplished player, comparatively unscathed by injury and with many miles left on the clock, Bell was a certainty to play. So in order to find room for Pietersen, England would have had to prefer him to either Root or Ballance - the two brightest young hopes of English cricket.

We will come to what actually happened in a moment. First, what was the information available at the time, before the start of the 2014 home Tests? Ballance had just made his debut, in the uniquely brutal circumstances of a 5-0 whitewash in Australia. Despite not making a big score, he looked at home - "There's something there," most people thought. It would have been a ruthless decision to discard him after just one match - perhaps one with damaging long-term consequences.

In the case of Root, it was more a question of making sure that a precious resource was nurtured in the best surroundings. In his short career, Root had already been up and down the batting order like a yo-yo, an experience so disorientating that even Root, a notably resilient character, ended up out of form and dropped. But no one seriously envisaged an England team without Root - not in the long, medium or short term. For Root the sine qua non was a spell in a settled position, preferably at No. 5, where he enjoyed such exceptional success in his early Tests.

What of Pietersen? No one admired Pietersen at his best more than this columnist (as I explored here). What was the likelihood, however, of Pietersen being at his best in 2014? His long-term knee injury had caused him visible anguish throughout the winter Ashes series. More ominously there were signs that his powers were in decline. True, they had once bordered on the miraculous. Nevertheless, downwards is downwards.

Let's be scrupulously fair and widen the period of evidence well beyond the anomaly of facing Mitchell Johnson's thunderbolts in 2013-14. In his last 16 Tests, Pietersen averaged 36. In his final 54 Tests, he averaged 43 with seven hundreds. That sounds healthy enough. But compare it to his first 50 Tests, with 16 hundreds at an average of over 50. Remarkably for a player of such audacious talent and unique style, Pietersen's career was actually very predictable: a high plateau followed by a gradual falling off. In broad terms, there were very few oscillations. Beneath all the headlines, when told in numbers, the story is actually very simple.

Now for the counter-factual: how would England's summer have fared with Pietersen instead of Root or Ballance? Root scored 777 runs at an average of 97. Ballance has accumulated 704 runs at 70. Both were absolutely central to England's turnaround. It is hard to see England beating India 3-1 without them. Their runs first steadied then galvanised English cricket when it was reeling and on the ropes.

Theoretically, of course, it is possible that Pietersen might have done even better. But what pointers can we follow from his actual performances over the same period of time? He has not played a single first-class match. Instead he has played only T20. Even specialising in one form hasn't helped. All taken together (the T20 Blast, the Caribbean Premier League and the IPL), Pietersen averages in the mid-20s in 2014, significantly below his career T20 record. Moreover, many of his performances this summer have happened under the tutelage of his personal mentor - Graham Ford, who happens to be Surrey's head coach. Playing county cricket in his home city of London, watched by his preferred choice of coach, conditions were tailor-made for a bumper summer of runs - and yet it hasn't happened.

The youth-led environment of the England team is unlikely to have suited Pietersen so well. After all, it was a clash with Peter Moores, now restored as head coach, that led to Pietersen's sacking as England captain in 2008. And Pietersen's relationship with Alastair Cook had disintegrated by the end of the 2013-14 Ashes. Instead of playing in the welcoming atmosphere of Ford's Surrey, Pietersen would have found himself in an environment prickly with personal baggage.

So while we cannot know for certain how many runs he would have scored, we can deduce with total confidence that if Pietersen had played instead of either Ballance and Root, all available evidence suggests it is likely that the England team would have been weaker rather than stronger.

Nonetheless, the "Bring back KP!" lobby (though temporarily silenced) has had a very noisy summer. Pietersen has been offered every kind of platform to make his case, including a newspaper column. After the series defeat against Sri Lanka, the front page of his paper's sport supplement proudly announced: "How to fix England - by Kevin Pietersen." All this has been magnified by various social-media storms and campaigns on Pietersen's behalf.

The target of all this, of course, has been Cook. Even shrewd judges perceived Cook's mid-season struggles as a direct consequence of the sacking of Pietersen. But while the target was Cook, the victim of the "Bring back KP!" campaign has been Pietersen himself.

The media had things upside-down. It was imagined that England's decision to take the high moral ground in its sacking of Pietersen (by citing the importance of "team ethics") had accidentally but cruelly burdened Cook with an extra pressure - as though an already decent man had to carry an unnecessary moral weight.

In fact, it was the other way around. The anti-Cook brigade, by citing Pietersen as the saviour in waiting, accidentally burdened their own man - even as he struggled for runs in T20 leagues around the world.

I hope the situation is remedied. Pietersen deserves to be remembered as a thrilling, world-beating batsman, arguably England's finest in living memory. He will not be the last maverick to end his international career in an imperfect way. In time, if he exercises restraint and exhibits more magnanimity, memories of his pomp will haze over the uncomfortable final chapter of his England career.

Last week it was good to hear Sir John Major commenting on the death of the former Irish premier Albert Reynolds, a political contemporary of Major's. No politician suffered worse treatment from his critics than Major. And none has enjoyed a greater bounce in popularity since leaving office. The secret: he has kept a benevolent and dignified distance from current events.

It is true that Major and Pietersen could hardly be more different as people. But Major, as a lifelong Surrey fan, is ideally placed to pass on some tips.