LONDON, Jan 5 (Reuters) - Alexis Sanchez scored a hat-trick to lift Barcelona to a 4-0 win over Elche which took them back to the top of La Liga on Sunday.
Italian Serie A leaders Juventus ended second-placed AS Roma's unbeaten run with an emphatic 3-0 win to go eight points clear at the top as the visitors had two men sent off in less than a minute.
English champions Manchester United suffered a 2-1 home defeat by Swansea City in the FA Cup third round and Premier League leaders Arsenal beat north London rivals Tottenham Hotspur 2-0.
An Alexis Sanchez hat-trick helped Barcelona beat Elche 4-0 and put them top of La Liga on goal difference ahead of Atletico Madrid who overcame Malaga 1-0.
Despite missing Lionel Messi and Neymar, it was one-way traffic for Barca who took the lead early on through Sanchez and Pedro was also on target after 15 minutes.
Xavi Hernandez missed a penalty before Sanchez added another and completed his hat-trick with a free kick.
It was harder work for Atletico to overcome a defensive Malaga but they eventually broke the deadlock through Koke in the second half.
Barca and Atletico both have 49 points, eight more than third-placed Real Madrid, who face Celta Vigo on Monday
Champions Manchester United slumped to a 2-1 home defeat by Swansea City in the FA Cup third round.
Wilfried Bony's 90th-minute header condemned United to their fourth defeat at Old Trafford in six matches and heaped the pressure on manager David Moyes.
Goals by Santi Cazorla and Tomas Rosicky fired Premier League leaders Arsenal to a 2-0 win over local rivals Tottenham Hotspur and Chelsea and Liverpool also reached the fourth round.
Manchester City were held to a 1-1 draw at Blackburn Rovers.
Serie A leaders Juventus ended second-placed AS Roma's unbeaten run with an emphatic 3-0 win on Sunday to go eight points clear at the top as the visitors had two men sent off in less than 60 seconds.
Arturo Vidal gave Juventus the lead in the 17th minute and Leonardo Bonucci turned in Andrea Pirlo's free kick three minutes after halftime to put the hosts in control.
Roma imploded late in the game after Daniele De Rossi was sent off for a two-footed lunged tackle on Giorgio Chiellini in the 75th minute.
Pirlo floated over another majestic free kick, Bonucci headed towards goal and Leandro Castan punched the ball away and was sent off. Mirko Vucinic fired in the penalty to complete the scoring and seal Juve's 10th successive league win.
Juventus have 49 points from 18 games with Roma on 41.
Monaco twice came from behind as they struggled past third division side Vannes OC to reach the last 32 of the French Cup with a 3-2 away win on Sunday.
Yannick Ferreira Carrasco netted the winner four minutes from time after Radamel Falcao and James Rodriguez had cancelled our the locals' advantage.
Lorient were the only Ligue 1 team to be eliminated by lower division opponents as they slumped to a 1-0 defeat at amateurs Yzeure, who play in the fourth division.
Paris St Germain's game at Stade Brest, which was scheduled on Saturday, was postponed until Tuesday (1915 GMT) because of bad weather.
(Editing by Ed Osmond)