Zanetti's goal, which came with five minutes remaining and involved a mazy run from a deep position, put Inter on top with 17 points from eight matches, one ahead of Juve and two clear of Vicenza.
Vicenza have never gone better than runners-up in Serie A in 92 years but, until Zanetti's late goal for Inter, they briefly threatened to go top with their 2-0 win at Lazio, still reeling from their 5-3 Uefa Cup defeat at Tenerife. Lazio hit the woodwork three times before Giampiero Maini sealed Vicenza's victory.
Juventus coach Marcello Lippi blamed his side's indifferent performace in Turin on fatigue. The European champions struggled to break down Napoli's defence in the first half, relying on a mistake from goalkeeper Giuseppe Taglialatela for Zinedine Zidane's opener in the 43rd minute - the Frenchman's second goal in three league matches. Alfredo Aglietti claimed a deserved equaliser for Napoli.
Roberto Mancini, the most prolific striker in Italian football with 130 goals, celebrated his 400th game and possibly last match for Sampdoria - he is rumoured to be joining Inter - with two goals in a 3-0 home win over Piacenza. Sampdoria are now level third with Milan and Bologna, 3-2 winners over Roma.
Gianluigi Lentini arrived at Milan in 1992 as the world's most expensive player but left this year never having fulfilled his potential after nearly losing his life in a car accident. Yesterday he reminded Milan of what they are missing by setting up Felippo Inzaghi's 21st-minute opener with a mesmerising run. Demetrio Albertini struck the equaliser.
VfB Stuttgart missed out on a chance to overtake Bayern Munich at the top of the German League when they lost 2-1 at lowly St Pauli. Christian Springer scored both goals for the unfashionable Hamburg side. The defeat left the 1992 champions in second place on 27 points from 13 matches, one point behind Bayern, who drew 1-1 with local rivals 1860 Munich on Friday. Borussia Dortmund, 2-1 losers at home to Atletico Madrid in the Champions' League in midweek, bounced back with a 3-1 victory at Schalke before 71,000 fans.
Two goals by the teenager Thierry Henry helped Monaco crush Bordeaux 3-1 and take them into a challenging position at the top of the French League. Henry is understood to be attracting several big European clubs, including Real Madrid.
The three main contenders for the Dutch title, PSV Eindhoven, Feyenoord and Ajax, all won away from home, leaving PSV still on top by seven points, which should ease the pain of their exit from the Cup-Winners' Cup.