Inter slumped to a 3-0 defeat in their top of the table clash at Juventus, thanks to an Andres Guglielminpietro own goal and strikes from Pavel Nedved and Mauro Camoranesi, leaving them three points behind the Turin team at the top of Serie A.
Afterwards disappointed Inter manager Hector Cuper admitted: "Juventus have handed us a massive defeat.
"It's obviously a big setback and the most important thing to work on right now is the psychological affects this result will have on our players.
"The game was won in midfield. After the second goal, we lacked composure.
"I made the decisions and I was convinced that they were right. Responsibility for this defeat is mine.
"We must now face the next game with courage."
In Spain Barcelona led twice at Osasuna only to come away with a 2-2 draw.
Javier Saviola opened the scoring for Barca after 61 minutes only for Ivan Roasado to equalise.
Barca thought they had clinched all three points when Luis Enrique put them in front with just five minutes to play, only for Gerardo Rivero to score a scrappy stoppage time equaliser for the home side.
Bayer Leverkusen climbed to 12th in the Bundesliga with a 3-0 home win over Werder Bremen, thanks to goals from Daniel Bierofka, Sebastian Schoof and Juan.