Where Newcastle United are concerned, the norms can usually be ignored.
Normally, new managers enjoy a honeymoon period, immunity from blame for defeat often accompanied by an upturn in results. Normally a regime begins with widespread expectation that it will last for at least three years.
Maybe five. The prospect of the team the latest appointment could construct and what they might achieve is, to many, mouth-watering.
But at a club in a state of permanent crisis, Graeme Souness has enjoyed none of these advantages. The presumption throughout has been that his is a short-term tenure, whether or not a successor has been identified.
Forceful as the Scot's glare is, his grip on the reins of power has never appeared other than shaky, never more than two matches away from a must-win game. At a club where factions rule, Souness was quick to ally himself with the most powerful, that of Alan Shearer. And after enticing Scott Parker and Michael Owen to St James' Park, perhaps the Newcastle captain should eschew punditry and management for a second career in the PR industry in Tyneside.
Even Shearer's persuasive powers, however, have not protected Souness. Nor, indeed, did his 200th Newcastle goal, the only measure of separating one of the Premiership's most expensively assembled sides from League Two Mansfield on Saturday.
It may not buy Souness a stay of execution in the face of vocal opposition, even if the urgency of the advocates of change is hard to explain. Relegation barely features on Newcastle's radar, while only the serial optimists would anticipate that another manager could deliver European qualification or FA Cup success this season.
But hope, rarely in short supply among the Newcastle support, was fractured along with Michael Owen's metatarsal. It may yield benefits for Owen in the World Cup, but it was a bad break for Souness. And when even the long suffering lose hope, change appears inevitable.
In even the most cursory analysis of Newcastle, however, it is evident that some problems predate Souness' appointment, and will probably outlive his dismissal, whenever it comes.
Shearer directed his most pertinent question at Glenn Hoddle - 'have you ever thought it could be you?' - but Freddy Shepherd would make just as appropriate a target; managers come and go but chairmen, from Doug Ellis to Rupert Lowe, Milan Mandaric and Shepherd, remain.
Poor defending and extravagant spending in the transfer market, too, were features of Newcastle prior to the arrival of Souness. Injuries, the excuse cited most often by the Newcastle manager (and, in his absence, his increasingly visible assistant Alan Murray), are no novelty either. Indeed, with a list of absentees consistently among the lengthiest in the country, Souness even changed training facilities in a bid to reduce the numbers of the walking wounded.
But, enjoying greater resources than the majority of their rivals, Newcastle should be better equipped to cope with them. If they are not, it merely serves to highlight Souness' transfer dealings. His £50 million outlay in 2005 was exceeded only, inevitably, by Chelsea, yet Newcastle trail Bolton and Blackburn, each luring an assortment of free transfers and loan signings to East Lancashire, and the promoted pair of Wigan and West Ham.
For the most part, Souness' signings are evidence of ambition, even if that subsequently serves to emphasise underachievement. He has plenty to show for his investment, too: Parker is an unqualified success and the envy of at least half the Premier League; Owen has maintained an excellent ratio of goals per game, though it is to Newcastle's detriment that there have been too few of the latter; as Sunderland can testify, Emre, another sporadic presence, has a wonderful left foot; and Nolberto Solano's has been a happy homecoming.
Yet, as with Owen and Emre, questions can be asked about the need to buy the popular Peruvian. James Milner has excelled in exile at Aston Villa, just as Jermaine Jenas, disenchanted by life on Tyneside, has contributed to Tottenham's campaign for a Champions League place.
And Craig Bellamy, valued at little more than a third of Owen by Newcastle's powerbrokers, has helped an unheralded Blackburn team outperform Newcastle. His departure, both a consequence of Souness' insistence on confrontation and his marriage of convenience with Shearer, has deprived Newcastle of the options blistering pace provide.
Selling Bellamy and Jenas brought in £14 million - the Scot's net spending is nearer £35 million - but while his attacking signings have generally entertained (with the exception of Albert Luque who, like bullfighting, appears hugely popular in Spain but certainly doesn't travel well), the entertainment provided by his defensive acquisitions has been unintentional.
At £8 million, Jean-Alain Boumsong ranks among the Premiership's costliest defenders. As a France international, he should be one of the best. Yet, despite Boumsong's power and pace, he has simpler failings, in passing and positioning. Why, with no other bidders last January, did he command such an exorbitant fee?
His partnership with Titus Bramble, subject to a laughing ovation when introduced at Liverpool, is the fourth most expensive in Premiership defences, and also the most error-prone. Bramble's misplaced passes have contributed to goals for Chelsea and Middlesbrough in recent weeks; Boumsong, supposedly the senior defender, has been just as culpable.
At left back, Celestine Babayaro has been almost as suspect as the central defenders; it is no surprise that Souness is credited with an interest in Wayne Bridge. Moreover, his only defensive addition in the summer was Craig Moore, further proof of his weakness for all things Rangers and, in any case, fit about as often as Kieron Dyer.
His absence, among other things, prompted Lee Clark and Steve Harper to suggest Newcastle are cursed. A more logical suggestion would be that they are unable to defend.
And when Graeme Souness, as appears increasingly likely, joins the litany of former Newcastle managers, he may reflect on the wisdom of his signings 12 months ago, constructing a new defence that proved just as leaky as their predecessors.
But at Newcastle United, the faces change, but the problems stay the same.
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