Descriptions such as 'enigma' and 'mercurial' are often applied to flair players who specialise in the unpredictable. They are immediately applied to Luis Garcia, whose blend of the mediocre and the brilliant can baffle, yet, to his superiors, his team-mate Peter Crouch can appear just as mysterious.
Certainly there are few forwards who, despite scoring, are demoted to the bench with such regularity or who seem so capable of confounding the expectations of his managers, whether for club or country.
Indeed, he has long done so: few anticipated Crouch joining the distinguished list of Liverpool forwards and those who, like Graham Taylor and Jamie Redknapp, regarded him as a future England player were very much in the minority.
For England, Wayne Rooney is the player around whom the attack is constructed. For Liverpool, Dirk Kuyt has quickly become, unequivocally, the first choice, with Crouch and Craig Bellamy, offering very different options, competing to partner him.
His height and the particular challenges it offers make him an ideal substitute, offering the potential to alter the complexion of a game: not for Crouch the easier life with a guaranteed start elsewhere. Yet, to his advocates, a station on the bench is unfair.
Because, since he belatedly broke his Liverpool duck against Wigan last December, Crouch has scored 31 goals in 12 months for club and country. They are superb statistics - even if preceded by a five-month drought - but very much open to interpretation.
His international tally was aided by five against the minnows of Andorra and Jamaica, while his solitary World Cup strike, though undeniably useful, came against Trinidad & Tobago, the lowest ranked team in the tournament. In the Premiership this season, meanwhile, Crouch has only scored twice in 12 games, hardly suggesting he is an unstoppable finisher.
Nor do his performances in the biggest games. Crouch was utterly ineffectual at Arsenal and in Liverpool's insipid derby defeat to Everton. He may cherish his FA Cup winner's medal, but his display in the final is unlikely to evoke such pleasant memories.
So is he a flat-track bully? Continental defences may beg to differ. The peculiarities of his unique frame seem to pose them more problems. Five European goals already this campaign indicates the Champions League is not just the domain of the technically gifted midfielders.
So confusion appears to afflict Crouch's managers. After his winner in Macedonia, Steve McClaren suggested he was nigh-on undroppable. Two games later, he was omitted against Holland and the suggestion is that, had Andrew Johnson been fit enough to face Croatia, Crouch would have been demoted sooner.
It encapsulates Crouch: the enthusiasm, the awkward gait, the advantages his unusual physique gives him and the sense that he had almost achieved his purpose, but not quite.
It is worth remembering that Crouch did not figure in McClaren's initial selection to face Greece. Had Dean Ashton not injured an ankle in training, he would have partnered Jermain Defoe.
Instead, Crouch scored twice, aided by a compliant Greek defence, and now his goals-per-game ratio in international football bears greater similarity with Jimmy Greaves' record than those of Rooney or Michael Owen.
There was the incongruous sight of Crouch as the leading scorer in international football in 2006; more facetiously, one newspaper calculated that if he continued scoring at the same rate, he would end his England career with 264 goals.
That was before he was dropped. Perversely, his place in the Liverpool team never seemed more secure than when Crouch wasn't scoring. In part, it is a consequence of Rafael Benitez's obstinate streak; he is steadfast in his loyalty to one of his out-of-form or under-pressure charges, but reluctant to board a bandwagon championing popular players.
Praise is invariably qualified by reminders that improvement is essential or, as Crouch can testify, experience of life among the replacements.
Outside Anfield, criticism and mockery have been more common reactions to Crouch. He was part of the goal-shy Liverpool attack that was ruthlessly destroyed in the summer. That he stayed while Djibril Cisse and Fernando Morientes departed is surely a consequence of his commitment to the team ethic as well as the improbability of an identikit replacement for Crouch existing anywhere.
Indeed, there is an element of the unorthodox in everything Crouch does.
Witness, for instance, a chance he supplied for Steven Gerrard against PSV Eindhoven. Slipping when receiving Kuyt's pass, he contrived to extend a telescopic leg and divert the ball towards his captain, without placing it where Gerrard wanted it. It encapsulated Crouch: the enthusiasm, the awkward gait, the advantages his unusual physique gives him and the sense that he had almost achieved his purpose, but not quite.
Not that all his problems are of his own making. As Jan Kromkamp pointed out, teams often resort to aiming long balls in his direction. And his most severe limitation is incurable: a lack of pace.
It was apparent when he was partnered with Robbie Fowler in the Liverpool derby and by England's inability to stretch opponents when he was in harness with Rooney, whose fondness for a speedier accomplice in attack is becoming apparent.
So, for England at least, it is back to the bench for the unfathomable Crouch. But, unlike many supposed enigmas, Crouch's unpredictability cannot be attributed to his attitude; indeed, without his willingness to work, Liverpool and England would have turned to others.
But if Messrs McClaren and Benitez seem undecided on his merits, they are not alone: seven clubs in as many years suggests other managers were equally divided.
Having made the journey from Aston Villa reserves to Liverpool and England in a year - via Southampton and relegation - it is hard to know what to expect next from Crouch.
For a unique player, there is no precedent and no career path set in stone: in this, as in much else, Crouch is unpredictable.