Kevin Pietersen has divided opinion from the moment he jacked in his lot with South Africa and made his great trek north in the summer of 2000 to launch his new life as a global sporting phenomenon. But right at this moment his staggering self-belief is flagging like never before. It's not so much the runs that are the issue, but the love. He's feeling unappreciated, and his discontent is corrosive.

Barely a day has gone by this week without Pietersen hitting the headlines for what he's said, or what he's done, or what he's said and done. One minute he's threatening to "do a Robinho" and flee an unhappy tour (a line that sounds sensational only when taken out of its original context), the next he's leaving the field with back spasms while bowling against a man he accused of hypochondria, Shivnarine Chanderpaul. It's a state of affairs that lends weight to the impression of a team in disarray. Pietersen is England's kingpin, and right now he's feeling skittled.

Some people will never understand what makes Pietersen tick, and his non-English origins are always on hand to provide his critics with ammunition, as the man himself admitted in the latest of a string of soul-baring interviews this week. "I think I'm going to have to live with that my whole career," he said. "I lived with that on Friday when we played a poor game of cricket and I got comments about South Africa. I deal with that on a daily basis and that's just the way it is, unfortunately."

And yet, less than 12 months have elapsed since Pietersen leant back on the sofa at the MCC museum and declared to the waiting press that he had "never felt so loved" by the English public, having just marked his first Test against his former countrymen with his 14th century. It was a telling choice of phrase from a man who, for all his awkwardness, seeks acceptance every bit as much as fame and fortune. Before that series was out, Pietersen had been named England captain, which he marked with a further century in a victorious maiden Test in charge, closely followed by four straight victories in a one-day campaign of greater intensity than England had shown for a decade.

The Peter Moores debacle brought a disastrous halt to that momentum, but to question Pietersen's commitment to England is both harsh and passé. He has never missed a single Test match since making his England debut in 2005. He's played in every single one of England's 15 Twenty20 internationals as well, and his last break from the ODI circuit came ahead of the World Cup in 2007, when he suffered a cracked rib while facing up to Glenn McGrath in Melbourne. His subsequent absence from England's next nine matches of the CB Series is the longest time away from the limelight he has had in four-and-a-half years as an international superstar.

Aside from Paul Collingwood, no one else in the squad comes close to matching that attendance record. Andrew Flintoff has played just 28 Tests in the same period, while the current captain, Andrew Strauss, was dropped for the tour of Sri Lanka in 2007-08, and had not played ODI cricket for two years until the start of the current campaign. Those who question Pietersen's commitment to England emphatically miss the point. He's scored nearly 8000 runs in eight countries including 23 centuries since his switch of allegiance, averaging 51 and 46 respectively in Tests and ODIs. He owes his adopted country nothing.

His country, on the other hand, owes him plenty. The cack-handed manner in which Pietersen was stripped of the England captaincy would irk even men with lesser tendencies towards ego-mania. One minute he was being asked how, in his valued opinion, the England team could be improved; the next he had offered his (admittedly drastic) solution, and found himself being drop-kicked out of office after his confidential comments had been leaked to the media.

After that episode, some feared Pietersen would flounce around the Caribbean like the spoiled brat he is perceived to be, or even decline to tour, and secure a full-fat contract with the IPL instead, but not a bit of it. He got straight back into training, scored a century in England's first warm-up game, in St Kitts, and but for an ill-judged stroke at Sabina Park that detracted from the determination that had preceded it, would have added a hundred in his first Test back in the ranks. Even when he did reach three figures in a superb final-morning onslaught in Trinidad, the fact that England fell one wicket short of squaring the series was used as further spurious proof that he's not a team player. It was Strauss who declined to declare before lunch that day, not the man in the middle.

"Those who question Pietersen's commitment to England emphatically miss the point. He's scored nearly 8000 runs in eight countries including 23 centuries since his switch of allegiance, averaging 51 and 46 respectively in Tests and ODIs. He owes his adopted country nothing"

There's no question that Pietersen is feeling the burn of touring life like never before. To a man, his England team-mates have spoken of his unstinting professionalism in the past 11 weeks, but the humiliation of his return to the ranks has melded with an England performance that has plumbed some spectacular depths. One of the benefits of Pietersen's promotion to the captaincy was that it provided an outlet for his excessive energies. Now, instead of being driven by responsibility to ever greater heights, he's being tipped by frustration ever closer to the edge.

Burn-out is a phrase that is used sparingly in Pietersen's presence, because as he himself recognised during the Oval Test last summer, he's got a finite window of opportunity as an elite athlete, and as a man in a rush to succeed, he is determined not to pass up a single opportunity - including the small matter of the IPL in a fortnight's time. His sojourn in South Africa is yet another reason why sympathy for his plight will be in short supply.

And yet, it should not be ignored how devastating the pressures can be on the key men in England's set-up. In recent years Graham Thorpe and Marcus Trescothick both succumbed to the pressures of being on duty 12 months a year. The common denominator is that they, like Pietersen, were undroppable in all forms of the game, and therefore did not get a break until the day they snapped.

Pietersen has said that never again will he go 11 weeks without seeing his wife, Jessica, and while it is easy to be cynical about celebrity love stories, it's not impossible that he really does miss her. The fact that Pietersen wanted to fly home to watch her take part in the finals of Dancing on Ice is the sort of cloying detail that we really could have done without, but as he once said, he is fortunate to have a wife who has been in the celebrity spotlight longer than he has, and therefore understands the pressures like no one else.

Pressure has been the life-blood of Pietersen's career, from his sensational first tour to South Africa in 2004-05, right through to the tour-salvaging performance he is surely plotting in St Lucia right now. Even when he endured a rare trough in Sri Lanka and New Zealand last winter, he still fronted up with the performance that won the series, a century in Napier last March, after his colleagues had stumbled to 4 for 3. But you have to wonder what his wife's advice will be when he does finally get home. It's been a draining year already, but the contests that matter are still to come.