Spanish leaders Barcelona suffered a shock 3-0 defeat at Villarreal as Juventus opened a four-point gap at the top of Serie A with a 4-2 win over Livorno on Sunday.
AC Milan were held to a 0-0 draw at Palermo to leave Juve clear at the top, but the most remarkable match of the weekend involved Inter, who scored three goals in the final seven minutes to claim a thrilling 3-2 victory over Sampdoria.
The top-flight clubs in England and France began their domestic Cup campaigns, with holders Manchester United held to a 0-0 draw by minor league Exeter City and Olympique Marseille falling at the first hurdle.
Italy winger Mauro Camoranesi scored twice for Juventus and Sweden striker Zlatan Ibrahimovic once after Alessandro del Piero's header gave them an early lead against Livorno.
Juventus have 43 points from 18 matches, AC Milan 39, Udinese, 2-0 winners over Cagliari, 34 and Inter 30.
Inter looked to be heading for their first league defeat of the season when Vitali Kutuzov put Sampdoria 2-0 ahead in the 82nd minute.
Obafemi Martens pulled one back six minutes later, however, and stoppage-time goals by strikers Christian Vieri and Alvaro Recoba completed a remarkable comeback.
Barcelona suffered only their second Spanish Primera Liga defeat of the season as two goals by Uruguayan striker Diego Forlan and one from Gonzalo Rodriguez earned Villarreal a deserved victory.
Forlan's swerving 20-metre strike gave the hosts a halftime lead, Rodriguez doubled that with a neat close-range finish and Forlan sealed an emphatic victory three minutes from time.
Barca's lead was cut to seven points by Real Madrid, who beat their city rivals Atletico 3-0, and champions Valencia, who defeated Levante 2-1 on Saturday. Espanyol are a further two points back in fourth following their 4-1 win over Osasuna.
Real had Brazilian striker Ronaldo and goalkeeper Iker Casillas to thank for their derby win.
BRILLIANT DISPLAY
Ronaldo grabbed a coolly taken double from his only two chances, while Casillas produced a brilliant display between the posts to end Atletico's unbeaten home record this season.
England's FA Cup produced upsets as usual, with pride of place going to Exeter's heroic 0-0 draw at Manchester United's Old Trafford fortress.
The record 11-times Cup winners fielded a severely depleted team and manager Alex Ferguson apologised to United's fans for an abject performance, which sets up a replay at Exeter.
United will at least be in Monday's fourth-round draw unlike four of their Premier League rivals.
Aston Villa lost 3-1 at Sheffield United, Manchester City went down 1-0 at Oldham Athletic, Norwich City were beaten 1-0 by West Ham United, and Crystal Palace were knocked out 2-1 by Sunderland.
League leaders Chelsea came from behind to beat Scunthorpe United 3-1, champions Arsenal also recovered from conceding the first goal to defeat Stoke City 2-1, and Newcastle United ended the dreams of minor league Yeading with a 2-0 win.
The French Cup also threw up surprises as Olympique Marseille and Saint-Etienne were knocked out in the first round.
Marseille's troubled season continued with a 3-2 home defeat to second division Angers, while Saint-Etienne lost 3-2 to third division Nimes.
French Ligue I clubs Strasbourg, Bastia and Istres also made early exits from the competition but there were no problems for league leaders Olympique Lyon, who cruised to a 2-0 win over fourth division Viry Chatillon.
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