Trabzonspor caused the shock of the night in the Champions League as they beat Inter Milan 1-0 in the San Siro.
Ondrej Celustka was the hero for the Turkish club with the only goal of the game in the 76th minute.
Trabzonspor only gained a spot in the group stage when national champions Fenerbahce were ejected after being accused of match-fixing.
Also in Group B, French champions Lille, with Joe Cole making his debut, drew 2-2 against CSKA Moscow.
In group C Basle earned a 2-1 victory over Otelul Galati.
Fabian Frei fired Basle in front on 39 minutes, but Marius Pena hit back for Galati just before the hour mark with a close-range finish.
Galati were reduced to ten men six minutes from time when Adrian Salageanu was sent off for bringing down Basle captain Maroc Streller inside the box and Alexander Frei slotted home the winning penalty.
CSKA Moscow hit back from 2-0 down to draw level with Lille in France. Seydou Doumbia scored twice - his second in injury time - to cancel out strikes from Moussa Sow and Benoit Pedretti.
In Group A Bayern Munich defeated Villarreal 2-0, the four-time champions ended their hosts' run of nine straight home European victories thanks to a goal in each half from Toni Kroos and Rafinha.
Real Madrid were without suspended coach Jose Mourinho and injured midfielder Kaka as they started their campaign in Group D with a narrow win over Dinamo Zagreb 1-0 in Croatia.
Angel di Maria struck the all-important goal in the 53rd minute for the Spanish giants who survived with 10 men for last 18 minutes after Marcelo's dismissal for a second yellow card.
Also in Group D, Ajax and Lyon played out a dull goalless draw in Amsterdam, with Michel Bastos coming closest to winning it for the French side.