A weekend of surprise results across Europe's big leagues saw Bayern Munich's unbeaten run come to an end, Napoli knocked off the top spot in Serie A and Manchester City toppled in the Premier League, where Leicester City are the new leaders.
Bundesliga leaders Bayern suffered their first league defeat of the season, losing to Borussia Moenchengladbach 3-1. Napoli lost 3-2 to Bologna while Manchester City were beaten 2-0 by Stoke City. Barcelona's La Liga lead was cut to two points after they could only draw with Valencia.
Surprise package Leicester City moved top as both Manchester clubs slipped up. Leicester won 3-0 at struggling Swansea City with a hat-trick by Algerian midfielder Riyad Mahrez.
Arsenal went second after beating Sunderland 3-1 as Manchester City dropped from first to third following a 2-0 defeat at Stoke.
Louis van Gaal's Manchester United failed to score again in another goalless draw, this time at home to West Ham United, and went down one place to fourth, three points behind the leaders.
Barcelona's lead was cut to two points when the Spanish and European champions conceded a late equaliser and were held to a 1-1 draw at Valencia.
Valencia's new coach Gary Neville was in the stands at the Mestalla stadium to watch forward Santi Mina power home a shot four minutes from time after Luis Suarez had fired Barca ahead just before the hour.
With 14 matches played, Atletico are two points behind Barca in second after they won 2-0 at Granada, with Real Madrid a further two points adrift in third following their 4-1 victory at home to Getafe.
Karim Benzema struck twice for Real, with Cristiano Ronaldo and Gareth Bale netting a goal apiece at the Bernabeu.
Champions Bayern Munich suffered a shock 3-1 loss at Borussia Moenchengladbach for their first league defeat of the season that cut their gap at the top to five points.
Gladbach struck three times in 14 minutes against the stunned visitors to win 3-1 and climb to third place on 26.
Borussia Dortmund, second on 35 points, needed a last-gasp goal from Shinji Kagawa to beat VfL Wolfsburg 2-1, with the Wolves slipping 10 points behind them in fifth.
Paris St Germain continued their stroll towards a fourth consecutive Ligue 1 title when Zlatan Ibrahimovic's double helped them to a 3-0 win at Nice.
PSG have 45 points from 17 games and lead second-placed Angers by 15 points after the promoted side added to Olympique Lyonnais's woes with a 2-0 win at Gerland.
Lyon dropped to fifth on 26 points.
Caen are second on 29 despite a 2-1 home defeat to fourth-placed Monaco (28) while Marseille's charge to the podium was checked with a 2-2 home draw against Montpellier that left them in ninth place.
Napoli suffered their first defeat since the opening day, losing 3-2 at Bologna, as Inter Milan ended the weekend top.
Fiorentina eased past Udinese 3-0 to go second.
Mattia Destro scored in each half for improving Bologna, either side of a Luca Rossettini header. Gonzalo Higuain scored two late goals for Napoli.
Milan Badelj, Josip Ilicic and Gonzalo Rodriguez were all on target for Fiorentina. Adem Ljajic scored for Inter Milan as they beat Genoa 1-0.
Inter have 33 points, Fiorentina 32 and Napoli 31.
Greece forward Christos Aravidis struck twice for AEK Athens as Gus Poyet's team beat AEL Kalloni 3-0 to lead the chase of runaway Super League leaders Olympiakos Piraeus.
Following Olympiakos's 4-3 win at Panthrakikos 24 hours earlier, the pressure was on AEK to pick up three points and keep the gap at 10 points.
AEK have 26 points points from 13 matches with Olympiakos out in front on 36 points.
Former European Cup winners Red Star Belgrade romped to a 7-2 away rout of neighbours Cukaricki to emulate a club record of 17 successive league wins after Argentine left back Luis Ibanez and 17-year-old striker Luka Jovic scored two goals each.
Red Star, European champions in 1991, stayed 19 points clear of closest rivals Borac Cacak, who ground out a 1-0 win at seventh-placed Javor Ivanjica.
Cukaricki slipped one place down to third while last season's champions Partizan Belgrade continued to struggle after a 2-0 home defeat by Vojvodina Novi Sad left them 24 points off the pace.
A 2-1 win over Charleroi put Club Bruges ahead in the Belgian league by a single goal from defending champions Ghent.
Jelle Vossen and Abdoulay Diaby scored either side of halftime and take Brugge to 37 points alongside Ghent, who were held to a 2-2 draw at home by Zulte Waregem.
Anderlecht failed to take advantage of a surprise loss for Oostende, who were beaten 2-1 at home by St Truiden. Instead a goalless drew at Racing Genk kept Anderlecht fourth on 33 points.
Champions Dinamo Zagreb, who have won the last 10 league titles, leapt back into the driving seat after a dramatic 2-1 home victory against traditional rivals Hajduk Split.
Dinamo are ahead of second-placed Rijeka on goal difference, with both sides on 39 points from 19 games after Rijeka were held to a goalless draw at sixth-placed Inter Zapresic.
Algeria striker El-Arabi Hilal Soudani netted a stoppage time winner for Dinamo after Hajduk midfielder Mijo Caktas cancelled out an early opener by Junior Fernandes.
Late goals from Paul Papp and Gregory Tade gave Steaua Bucharest coach Laurentiu Reghecampf a winning start in a 2-0 success over Universitatea Craiova.
Reghecampf took over on Thursday, three days after Mirel Radoi resigned following a poor run. Victory lifted the Romanian champions to fourth on 34 points from 21 matches. FC Astra, who drew 1-1 at CSMS Iasi on Sunday, top the standings on 42.