Real Madrid tumbled at Lyon 2-0 while AC Milan and Arsenal opened with impressive Champions League victories on Wednesday.
Manchester United also won, edging Celtic 3-2 at Old Trafford.
Six-time European champion Milan beat AEK Athens 3-0 and Arsenal, last season's runner-up, began its campaign with a 2-1 win at Hamburger SV despite the absence of the injured Thierry Henry.
Despite the return of former coach Fabio Capello and more big-name signings, Madrid looks no nearer to turning around its slump in European soccer. The nine-time champions still can't recapture the form that earned them three titles in five seasons from 1998-2002.
French champion Lyon could have been four goals up by halftime in a one-sided game at Stade Gerland. Fred scored in the 11th minute and Tiago added a second in the 31st while but Florent Malouda hit the crossbar and the Madrid defenders made frequent mistakes under pressure.
"We could have been further ahead at halftime," Lyon coach Gerard Houllier said.
In the other Group A game, Nicolae Dica scored twice as 1986 European Cup winner Steaua Bucharest beat Dynamo Kiev 4-1.
After Sorin Ghionea gave the Romanians a third-minute lead, Serhiy Rebrov replied for the hosts in the 16th. But Valentin Badea restored Steaua's lead in the 24th minute and Dica added two more to put his team in first place.
Jan Vennegoor of Hesselink gave Celtic a 21st-minute lead before more than 74,000 fans at Old Trafford in the first meeting of the two British teams.
Two-time champion United was lucky to get a penalty for Louis Saha to level, and the France striker made it 2-1.
But Japan midfielder Shunsuke Nakamura equalized two minutes before halftime with a direct free kick, and Ole Gunnar Solskjaer made it 3-2 for United early in the second half after Saha's shot had been blocked.
It was Solskjaer's first European competition goal in nearly three years.
"We should have scored a lot of goals," United manager Alex Ferguson said. "Celtic had a go all night. Some of the attacking play was very good and we should have scored a few goals. We did show our quality but there was a bit of slack defending."
The result put United in first place in Group F because FC Copenhagen and two-time European champion Benfica drew 0-0.
Arsenal was fortunate to go ahead in the 12th minute in Hamburg when goalkeeper Sacha Kirschstein was penalized and sent off for a trip and Brazil midfielder Gilberto Silva scored from the penalty spot.
Midfielder Tomasz Rosicky scored the second from 20m early in the second half for the Gunners. Boubacar Sanogo replied for Hamburg in the final minute.
"It was an important result and the performance was hard to judge after they had the goalkeeper sent off," Arsenal manager Arsene Wenger said. "It was like the Champions League final with the goalkeeper sent off for a foul."
Arsenal had goalkeeper Jens Lehmann sent off in the Champions League final loss to FC Barcelona.
A 0-0 draw between FC Porto and CSKA Moscow meant that Arsenal is in first place in Group G after the opening round of games.
Filippo Inzaghi, who scored in both legs of the qualifying round games against Red Star Belgrade, gave Milan a 17th-minute lead at San Siro and Yoann Gourcuff added a second minutes before halftime.
Kaka scored the third from the penalty spot in the 77th.
Anderlecht and Lille drew 1-1 in the other Group H match, with Nicolas Pareja giving the Belgian champions the lead four minutes before halftime. Substitute Nicolas Fauvergue replied for the French team in the 80th.
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