You can blame Didier Drogba's petulance, you can point to Branislav Ivanovic's lack of pace as Samuel Eto'o strode goalwards, you can wonder at the referee's inability to spot the outbreak of all-in wrestling that occurred every time Chelsea won a corner. But there is only one reason why Internazionale have progressed to the quarter finals of the Champions League while their city rivals were thumped last week: Inter know how to defend. Javier Zanetti, Maicon, Walter Samuel and the utterly peerless Lucio gave a masterclass in South American defensive techniques at Stamford Bridge last night.
At times their interceptions - particularly Samuel's to dispossess Florent Malouda after the Frenchman's breathtaking incursion into the penalty area, not bad for someone who appears to be 57 - were so astonishing you had to blink twice to accept they had happened. But mostly it was about positioning, about solidity, about marking. Drogba, the best centre-forward in world football his proponents claim, was made to look mute and ineffectual. The thought of that quartet up against Wayne Rooney or Zlatan Ibrahimovic in the next round should be enough to send football's accountants into ecstasy: who would not want to be there to witness that sort of duel?
And behind such a defence is the man who constructed it. Jose Mourinho has not got where he is today - sitting on a record of five domestic league titles in his last six years in management - without recognising the value of defence. While the man with whom he shares the San Siro dugout, Leonardo, looked increasingly helpless as Milan's leaden-footed back line was destroyed in Manchester last week, Mourinho could sit quietly purring as his back four smothered all adventure in West London last night. He may have forgotten to shave, but the old master of the Bridge had not forgotten to brief his defenders. They did precisely what he loves most in football: they made things certain. You get no flash from Mourinho teams, no fireworks or flamboyance. You just get results.
You wonder what Roman Abramovich must have made of it last night. He tired of the Portuguese's pragmatism when he was around. He craved a little flourish from his huge investment. He wanted rather more expression of character on the pitch and a little less ego in the dug out. So he axed the finest manager his club has ever had with predictable consequence: as Mourinho sneered before this game, while he has carried on winning things, Chelsea - with all the cash in the world to hire the best coaches and buy the best players - have landed just an FA Cup since he left three seasons ago.
And to be honest, they haven't looked any more exciting than they did before. It is still the core of Mourinho's efficient, clever team, now shorn of his attentive guidance. Another example - to add to Portsmouth's FA Cup victory, Leeds' Champions League adventure and Crystal Palace's team of the eighties - that in football you have to be careful what you wish for. Mourinho's team did last night what Italian sides used to do in European competition: they strangled the life out of their opponents. It may have been the case that there wasn't an Italian in the starting line up, but that was as Italian a performance as you could find. It restored a little respect back to Serie A which has been chastened by decline in European competition since Milan beat Liverpool in Istanbul five seasons ago.
The irony of Mourinho's position is that his success with Inter will probably hasten his departure from the country rather than seal his legacy. His is widely disliked there, treated with contempt by press and rival managers alike, apparently not particularly loved even in the Inter boardroom who have tired of his theatrical antics. More likely that performance last night will have further alerted those on the lookout for a new coach to his insistent claims. Real Madrid, Liverpool and Manchester City are all likely to be looking for a new man in the summer. And don't rule Chelsea out of the hunt, either. After last night, no-one involved at the club can any longer be in doubt about precisely what it is they have missed.