Anyone who predicted Hull City's victory at the Emirates Stadium on Saturday can congratulate themselves on their foresight, safe in the knowledge few others thought such an upset was possible. Yet there is a way of defeating Arsenal, and from that perspective Daniel Cousin's winner, headed in from a corner, was predictable. Sometimes the result can surprise, but the manner of it is all too obvious.
The Gunners' previous defeat this season occurred when Fulham's Brede Hangeland headed in a corner. They trailed, albeit briefly, at Bolton Wanderers when Kevin Davies headed in a corner. And as each of the three scorers was marked, not overly well, by William Gallas, the similarities continue.
Arsene Wenger promised changes and, obstinate as ever, duly removed some forcefulness from his side against Porto as Samir Nasri replaced Emmanuel Eboue. Others would remove Gallas, if not from the team then certainly from the captaincy.
Leadership does not require a physical presence, though it did Tony Adams and Patrick Vieira no harm, but Gallas appears better suited to the lieutenant's role, rather than that of the general. Responsibility sits particularly uneasily on his shoulders when the ball is directed towards Arsenal's six-yard box.
Whether the reserve centre-backs, Mikael Silvestre and Johan Djourou, would prove more diligent markers at set-pieces is a moot point, but both have the advantage of added inches. Arsenal, a team known for their athleticism, are short of height. Amidst a blur of sprinters, slow players, as Dennis Bergkamp was, have been very much a rarity, accepted for great technical gifts. Since Sol Campbell and Martin Keown left, however, such exemptions have not been made for taller but more limited footballers. And while Wenger's men have brought an element of track and field to the football pitch, they seem to have neglected the high jump, at least in their own penalty box.
It was said of Sir Alex Ferguson's first great Manchester United side that they could out-fight teams as well as out-play them. Arsenal, it appears, can out-pace them but not out-jump them. When strikers Robin van Persie and Emmanuel Adebayor are the two tallest players, that hardly aids the defence.
The problem can be psychological as well as physical. Kolo Toure, half of probably the Premier League's smallest central-defensive duo, admitted he was afraid of Hull.
Not for the first time, the unflashy attributes of the departed Gilberto Silva are missed. So, too, is Abou Diaby, whose resemblance to Vieira extends beyond his appearance. Denilson, Cesc Fabregas' Mini-Me, is excellent in possession, but ineffectual in his own box; a microcosm of Arsenal. They appear unwilling to sacrifice fluency for size, and that seems unlikely to change.
The next generation - Nasri, Theo Walcott, Carlos Vela, Aaron Ramsey and Jack Wilshere - all conform to the short, skilful type. While there is not a direct correlation between height and aerial ability, even some of the taller players in Arsenal's recent past - such as Thierry Henry - hardly relished defending corners.
Others compromise. Jose Mourinho, always the organiser, wanted at least four tall players on the pitch. Now, arguably, five defensive headers are required in the Premier League. Hull, for example, could send Cousin, Marlon King, Ian Ashbee, Kamil Zayette and Michael Turner forward at set-pieces and they are the rule, rather than the exception.
With apologies to those who favour metric measurements, it is no coincidence that in England, given the imperial system, the six-footers exert a hold on the imagination. The modern-day Wimbledon, Stoke, fielded 10 six-footers at times last season; Liam Lawrence, the comparative dwarf, was half an inch short and, in any case, took the free kicks and corners. A newcomer could be forgiven for thinking that the Potteries was a land of giants Gulliver discovered on his travels. There has long been a theory a promoted team would overcome Arsenal, but that side was expected to be Stoke.
And it is Arsenal's misfortune that possessing a contingent of players who experience high altitude every time they jump matters more in the Premier League than elsewhere. Barcelona's technical wizardry is evident whenever they have the ball, but they have been able to field footballers of the stature of Deco, Lionel Messi, Xavi and Andres Iniesta - plus such reluctant headers as Ronaldinho - in recent seasons.
England, in contrast, has a set-piece fixation. Arsenal, through Gallas and Adebayor, have even scored from several themselves, but that doesn't necessarily equip them to defend them. Wenger has said that he believes his current generation of technicians and speedsters have the potential to better the Invincibles of 2003/04. In terms of inventive, attacking football, marked by passing of both incision and imagination, he may be correct.
But the criteria are broader. The Invincibles contained giants such as Campbell and Vieira, men who could repel opponents whichever way they chose. The beatables could do with a fully-fit Diaby, as a midfield destroyer and a giant figure in his own box, and they could benefit from detailing someone other than Gallas with halting their opponents' finest header.
Arsenal swept Porto aside imperiously, but we can only say they have turned the corner when they are not panicked by corners. Because while it may be irrelevant for the purists, the moral of recent games is one pragmatists would endorse: size matters.