Leaders Chelsea were held to a 1-1 draw by Aston Villa in the English Premiership on Saturday, while Bolton Wanderers beat Liverpool 2-0 to move up to second.
Beginning the day two points clear of Manchester United and Portsmouth, Chelsea looked set for another victory when Didier Drogba put them ahead at Stamford Bridge after just one minute.
But Aston Villa, who have made a superb start to the season under new manager Martin O'Neill, hit back and Gabriel Agbonlahor headed them level on the stroke of half-time.
"The result is not fair. One team tried to win, the other tried to get a draw," Chelsea manager Jose Mourinho said.
"I think it was our best game of the season. We produced incredible football and I think 10 great chances. I wouldn't have been surprised if they had scored a winner at the end. It just wasn't our day," he said.
The result moved Chelsea two points clear of Bolton, who upset Liverpool with a typically physical performance at The Reebok.
Goals from Gary Speed and Ivan Campo gave the home side victory.
Eidur Gudjohnsen and Javier Saviola scored to help defending champion FC Barcelona defeat 10-man Athletic Bilbao 3-1 and take a three-point lead in the Spanish league on Saturday.
Gudjohnsen, replacing injured Samuel Eto'o, struck Barcelona's second goal from Xavi Hernandez's pinpoint pass in the 61st minute, while substitute Saviola added the third 16 minutes later to seal his team's victory on coach Frank Rijkaard's 44th birthday.
Saviola hadn't scored a league goal for Barcelona since 2004.
Bilbao took an early lead in the fifth-round game at its San Mames stadium through Fran Yeste but was then hit by the 19th-minute ejection of left back Javier Casas, and an own-goal by Ustaritz Aldekoaotalora just before the interval.