Napoli came back from a goal behind to take a 3-1 lead into the second leg of their Champions League second-round tie against Chelsea.
Chelsea - who had started the match with Ashley Cole, Michael Essien, Frank Lampard and Fernando Torres on the bench - had looked shaky in defence in the early stages of the match, but they took the lead on 27 minutes through Juan Mata.
The lead did not last long, Ezequiel Lavezzi curling the ball past Petr Cech for an equaliser 11 minutes later, and Edinson Cavani put the hosts in front when he used his shoulder to divert home in first-half injury time.
Chelsea looked dangerous in the second half and had numerous opportunities to get back on level terms, but a glaring error from David Luiz allowed Lavezzi to make it 3-1 on 65 minutes.
CSKA Moscow gave themselves hope after rescuing a late 1-1 draw in their match at home to Real Madrid.
Madrid, despite having to adapt to the freezing temperatures, had looked much the better side in the first half at the Luzhniki Stadium and got their reward when Cristiano Ronaldo netted a potentially crucial away goal on the half-volley on 28 minutes.
However, Moscow were much improved in the second half and got their reward in the 93rd minute when debutant Pontus Wernbloom volleyed home from close range.
Madrid host CSKA for the return leg at the Santiago Bernabeu on March 14.