Riot police were required outside the San Siro as fans protested at the club's current form.
Christian Abbiati saw red as AC Milan slumped to a 4-2 defeat against Parma.
Jurgen Klopp talked to supporters as Borussia Dortmund lost 2-1 to Borussia Mönchengladbach.
Riding the crest of a wave, Liverpool's Luis Suarez celebrated scoring against Manchester United.
Premier League leader Chelsea lost against Aston Villa as Jose Mourinho was sent to the stands.
Everton snatched victory in the 93rd minute against Cardiff City to add to the Welsh side's relegation woes.
Zlatan Ibrahimovic netted a brace as PSG continued its Ligue 1 dominance with a 2-0 win over Saint-Etienne.
Lionel Messi bagged a hat trick against Osasuna to become Barcelona's all-time top scorer.
Real Madrid retained its three-point lead thanks to Cristiano Ronaldo's 23rd-minute strike against Malaga.
Atleti edged a 1-0 win against Espanyol thanks to Diego Costa to keep pressure on Real Madrid.
Memphis Depay scored the winning goal for PSV against Vitesse in a vital Eredivisie clash.
On his record-tying appearance for Juventus (476) Gianluigi Buffon made a crucial penalty save.
Tottenham manager Tim Sherwood gritted his teeth after seeing his side lose 1-0 to local rival Arsenal.