AC Milan opened the defence of its Champions League title with a 2-1 win over Benfica on Tuesday afternoon, while Chelsea and 10-man Liverpool had to settle for 1-1 draws.
Nearly four months after Milan beat Liverpool to win its seventh European Cup, Andrea Pirlo scored one goal and set up the other in Milan.
"He is an irreplaceable player," Milan coach Carlo Ancelotti said. "He scored a goal, made an assist and directed the passing well."
In Group B, Canadian international goalkeeper Lars Hirschfeld helped Norwegian champion Rosenborg hold Chelsea to a draw in London.
Miika Koppinen gave the visitors the lead in the 24th minute at Stamford Bridge, beating John Terry to a cross and volleying the ball past Chelsea goalkeeper Petr Cech.
Andriy Shevchenko scored the second-half equalizer in the 52nd minute when he took a cross from Florent Malouda and headed it over Hirschfeld.
"I think they [Rosenborg] were not a problem, we were the problem," Chelsea manager Jose Mourinho said.
In Milan, Pirlo curled a free kick into the top left-hand corner in the ninth minute.
He then passed to Filippo Inzaghi in the 24th, and the striker beat Benfica goalkeeper Quim for his 60th goal in UEFA events, and 39th in Champions League play — two goals short of Gerd Muller's European record.
Second-half substitute Nuno Gomes tapped in a consolation goal for Benfica in injury time.
The win gives Milan three points in Group D, the same as Shakhtar Donetsk, which beat Celtic 2-0 in Donetsk, Ukraine, on Tuesday, with goals in the first eight minutes from Brandao and Cristiano Lucarelli.
Liverpool finished 1-1 at FC Porto.
Liverpool midfielder Jermaine Pennant was sent off in the 58th minute for a second yellow card.
Real Madrid defeated Werder Bremen 2-1 with a 74th-minute goal from Ruud van Nistelrooy, who also helped set up Raul Gonzalez for the Spanish club's first goal.
Also, it was Marseille 2, Besiktas 0; Schalke 0, Valencia 1; and Olympiakos 1, Lazio 1.
Milestonemarker for Van Nistelrooy
Raul gave Madrid the lead in the 16th minute after taking a low cross from Van Nistelrooy for his 57th Champions League goal.
Werder Bremen immediately levelled, when Boubacar Sanogo prodded the ball in from close range in the 17th.
Van Nistelrooy's winner was his 50th goal in the Champions League.
He slotted in a short pass from Raul to make up for missing a handful of chances in the match.
"The team worked for this win. They knew it wasn't going to be easy," Madrid coach Bernd Schuster said. "They worked, they fought.
"They did some things I liked a lot, some I didn't so much. But we deserved it in the end."
In the other Group C match, Luciano Zauri scored a late goal to help Lazio hold Olympiakos to a 1-1 draw.
Zauri beat the offside trap and slotted the ball past Olympiakos goalkeeper Antonis Nikopolidis in the 77th minute.
Olympiakos had gone ahead when Luciano Galletti scored in the 55th.
David Villa scored in the second half to give Valencia a 1-0 win at Schalke in Group B.
Villa scored against the run of play in the 63rd after collecting a long ball from Luis Miguel.
He outpaced Heiko Westermann and shook off a challenge from Schalke goalkeeper Manuel Neuer before slotting home.
Liverpool forced to level
Liverpool fell behind in Porto when goalkeeper Pepe Reina fouled Tarik Sektioui and Lucho Gonzalez converted a penalty kick in the eighth minute.
Dirk Kuyt headed in from close range in the 17th to level.
Steve Finnan sent in a cross from the right that was headed across the goal by Sami Hyypia to Kuyt.
"We are pleased because we played 30 minutes with 10 men," Kuyt said. "Porto is a really strong team.
"At least we didn't lose. If we can beat them at home, we will be OK."
Marseille beat Besiktas in the other Group A match, with second-half goals from Julien Rodriguez and Djibril Cisse.
Rodriguez scored from close range in the 76th after Samir Nasri's corner bounced back off the post and fell to his feet.
Cisse broke through in injury time and poked the ball inside the near post.