Football is a combination game. The bonds of trust and understanding between team-mates make as much of a difference as their abilities as individuals. Napoli's forwards, last night, had the benefit of those bonds. Chelsea's defence did not.
Ezequiel Lavezzi and Edinson Cavani, who scored all three Napoli goals between them, know each other's games with fraternal understanding. That pair, along with Marek Hamsik, whether running with or without the ball, know precisely where their team-mates will be and what they will do. Few teams outside of Barcelona can play with such cohesion or solidarity.
For Gary Cahill and David Luiz, though, this was just their third game together. Signed from Bolton and Benfica, they were strangers last night, the opposite of their opponents, troubled throughout by their knowing play.
If Chelsea had not been prepared for the instinctive brilliance of Lavezzi's movement, in as much as a back four of strangers can be, they would have known within the first minute. Both Cahill and Branislav Ivanovic had to hurriedly intervene in the opening minutes, with Lavezzi darting behind them.
But if there is one thing more dangerous than Lavezzi running off the ball, it is Lavezzi running on it. Dropping, receiving, turning and running is his natural game, and it was one of his first touches which released Gokhan Inler, who found Edinson Cavani burning in behind Cahill and shooting straight at Petr Cech. Only an off-side flag stopped Cavani from taking advantage of Lavezzi's perfect blind reverse pass.
For all these early discomforts, Chelsea took the lead thanks to an error at the other end. But Lavezzi, always teasing, always surprising, always out of reach, brought them level. He has an intuitive nose for space and danger, and he dropped off on to the edge of the box, receiving Cavani's pass. With a shift of the hips, he moved away from Ramires and Raul Meireles. Cahill, more worried about what was behind him, stood off. Lavezzi strummed the ball into the far corner.
But Cahill was right to be worried: the space in behind him was as dangerous as the space in front, as Cavani proved in first-half stoppage time. Inler swung in a perfect cross from the right, which Cahill negligently allowed to bounce yards from goal. Cavani's swooping far-post run surprised both Cahill and Ivanovic, and his right shoulder slammed the ball past Cech.
Again, Chelsea started to pass the ball well, but again, their centre-backs could not live with their hosts. The decisive goal came when Luiz was caught by surprise by Cavani. As ever, Lavezzi pulled away into space, Cavani knew where, and a simple finish followed the simple pass. Napoli should have scored a fourth, when Hamsik overlapped beyond Cavani, but Maggio's shot was blocked by Ashley Cole. Napoli will be disappointed not to have killed the tie.