There are caretaker, interim and acting managers, and then there is the most high-profile locum in world football. Guus Hiddink's temporary stint in charge of Chelsea begins in earnest at Villa Park on Saturday. It may only span 13 Premier League games but Hiddink, who has long displayed an ability to depart while leaving his employers wanting more, now carries the expectation of seismic change wherever he goes.
He is already the subject of scrutiny. The television cameras focused on the impassive Dutchman, next to a captivated, animated Roman Abramovich, during the FA Cup victory at Watford, though his was largely a watching brief. There have been (presumably fanciful) suggestions his ever-present scarf is lucky; along with, more logical theories that his presence galvanised Chelsea's reserves in their 6-0 victory on Monday night and thoughts that pairing Didier Drogba and Nicolas Anelka in training is a pointer to his team selection.
The serious judgements can begin this weekend. Hiddink is accustomed to being assessed on the basis of a handful of games in major tournaments; his reputation is often enhanced, but normally because of a few decisions. Chelsea presents another test of the international alchemist. Getting results around the world renders him both inspirational and enigmatic in the eyes of an English audience although, upon closer examination, some of Luiz Felipe Scolari's mystique faded.
Hence the SOS to a manager who seems to prefer each challenge to be vastly different from the previous. Hiddink has proved himself capable of rapidly transforming a team, but Chelsea's fortunes require immediate alteration. The encounter with Villa represents a pivotal game. Subdued as their recent showings have been, it was surely fear of fifth place and the Europa League that prompted the dismissal of Scolari.
And Abramovich's Chelsea are as unaccustomed to fifth as South Korea were to the World Cup semi-finals seven years ago. It is why Hiddink's latest career choice may be his riskiest. While there is no such thing as a no-lose job in football, he has been canny in his selection of roles. Taking South Korea and Australia further than they had ever been was aided by an undistinguished history. Russia had been in an extended malaise before his appointment. Fail at any and he would have merely been continuing a trend. Succeed and millions would marvel.
Chelsea, in contrast, have both a remarkable recent prowess and a disturbing underachievement in the last few months. It is a dangerous concoction for a manager. Get results and he is merely emulating most of his predecessors; flounder and he appears part of the problem. Unless he wins the Champions League, this season will still be less rewarding than those orchestrated by Jose Mourinho.
Much of the speculation will focus on Hiddink's initial selection. He is rarely predictable. There has been a flexibility in his approach that has enabled him to channel his players' attributes - the South Koreans' energy, the Australians' competitiveness and the Russians' technique - and adapt his tactics to suit them. But floundering teams can be more open to ideas and egos rarely mushroom in a losing side.
Stamford Bridge, however, seems to be the spiritual home of player power. Avram Grant failed to impress some, Scolari alienated others. There are individuals who are yet to be weaned away from Mourinho's methods or formation and several whose form was finer under the Portuguese. Some issues are constants - the overcrowding in the centre of midfield, the difficulty in allying Anelka with Drogba - and even a creative thinker like Hiddink may only resolve them with greater contributions from some of his most prominent players.
Should Chelsea follow Russia's lead and operate with a 4-1-3-2 system, for instance, it may permit him to unite Drogba and Anelka without asking either to operate as a winger; the downside may be that, as Scolari did, he relies upon the full-backs for width.
Playing the 3-4-3 that allowed South Korea to prosper could permit Hiddink's former PSV charge Alex to accompany John Terry and Ricardo Carvalho at the back when all are available, with Ashley Cole and Jose Bosingwa granted more advanced roles and the holding midfielder rendered surplus to requirements. A back three worked for Australia, too, though the sole starting striker in the Socceroos side appeared more a function of the presence of Harry Kewell and Tim Cahill to support Mark Viduka than dogma.
Hiddink, unlike the majority of his peers in the Premier League, has rarely used an orthodox 4-4-2. That ultimately worked for Ray Wilkins at Watford on Saturday; however, a shortage of natural wingers and a surfeit of central midfielders makes it hard for Hiddink to deploy it with his new charges. Like many Dutch managers, he is no stranger to 4-3-3, but Chelsea have stagnated in that system.
It is a consequence, in part, of individual failings. A catalyst is required to revive Ricardo Quaresma's career, to reinvigorate Drogba and Deco, to remind Florent Malouda he was once capable of playing in a World Cup final and to restore Michael Ballack to his dominant best. An injection of confidence is necessary to ensure a return to winning ways and, in turn, to forget the one who got away.
It may have been different with Robinho, and Scolari complained he had too few special players. With game-changing substitutions, unorthodox tactics and a capacity to extract more from his players than his predecessors did, Hiddink has pioneered the manager as match-winner. The paradox is that, with arguably the strongest squad he has inherited since he joined Real Madrid, he may have his stiffest task ahead of him if he is to emerge with his reputation as a miracle worker intact.