Manchester United midfielder Darren Fletcher returned as a late sub in their win at Old Trafford, while Chelsea and Celtic started their Champions League campaigns with draws.
Champions League round-up: Di Matteo hails 'big talent' Oscar on debut
Sir Alex Ferugson, the Manchester United manager, admits he should not have let Nani take the penalty he missed against Galatasary in their narrow victory at Old Trafford.
The Portuguese winger became the third United player to fail from the spot, and Ferguson said afterwards penalty duties should have fallen to Robin van Persie.
"I thought Robin should have taken it, to be honest with you," he said.
"I think we will have to decide before the game. That was my fault, I should have done that."
United could not build on their lead and Galatasaray, appearing in the Champions League for the first time in six years, were unlucky not to leave with a point after hitting the woodwork three times.
Nani made United work harder for their win when Muslera saved the Portuguese winger's feeble 53rd-minute penalty following a foul on Brazilian defender Rafael.
The result was Sir Alex Ferguson's 100th Champions League win, but the biggest cheer of the evening was for the return to action of Darren Fletcher for the first time in almost a year.
"The supporters recognise what a tough time he has had for the last year," Ferguson said. "They gave him a marvellous reception.
"He has been out of the game for a year it took him one or two minutes to get going but he can only be better after tonight."
In the group's other match Rafael Bastos scored twice against his former club Braga to put Romanian club Cluj at the top of the table.
Bastian Schweinsteiger and Bayern Munich cast aside the bitter memories of their Champions League final defeat in May to begin the campaign with a 2-1 Group F victory over Valencia.
Schweinsteiger, whose spot-kick miss in the final shootout allowed Chelsea to score and be crowned European champions, fired Bayern into the lead with a deflected shot in the 38th minute, much to the delight of the 68,000 sold-out crowd in Munich.
Midfielder Toni Kroos added a second when he scored with a 20-metre drive in the 76th minute.
Defensive-minded Valencia, in their first encounter with Bayern since losing to the Germans in the 2001 Champions League final, cut the deficit with a header from Nelson Valdez in stoppage time.
Bayern should then have made it 3-1 but substitute Mario Mandzukic saw his penalty saved by keeper Diego Alves after Adil Rami was sent off.
A remarkable three-goal salvo in the first half gave BATE Borisov their first-ever Champions League win, 3-1 at Lille, to leave the French club facing a huge task to rescue their campaign.
Aleksandr Volodko, Vitali Rodionov and Edgar Olekhnovich all found the net for the Belarusian side.
Juventus stunned holders Chelsea with a superb fightback to earn a 2-2 draw in their opening Group E match at Stamford Bridge.
Oscar had given the hosts a dream start with a stunning first-half double on his debut in the competition, but Antonio Conte's side exploited poor defending by the European Cup holders.
"We did during the game give the ball away a little bit too cheaply at times but I think we also played some good stuff tonight," Roberto Di Matteo, the Chelsea manager, said afterwards.
"It was a great debut for Oscar. I thought it was the right game to start him and he did a perfect job tactically.
"He scored two goals and the second one was a wonderful goal. He is a big talent. He has got a bit of everything.
"We shouldn't forget that he is still a young man - he is only 21 - but he is already quite established in his national team already."
A double from Armenian midfielder Henrik Mkhitaryan gave Ukrainian giants Shakhtar Donetsk a 2-0 win over Danish Champions League debutants Nordsjaelland in Group E.
Scottish champions Celtic claimed a goalless draw against Group G rivals Benfica in Glasgow on their spirited return to the competition.
Despite starting brightly Celtic failed to trouble Benfica goalkeeper Artur during the opening half, while alert work in the home goal by Fraser Foster kept the scores level.
"I hope that we gained a little bit more respect tonight from the footballing world," Neil Lennon, the Celtic manager, said afterwards.
"I think Benfica went into the game heavy favourites but I don't think you could call the game tonight.
"I think a draw was probably a fair result.
"It shows that we have a bit of depth to the squad and can compete at this level.
"We didn't work their keeper as much as we would have liked but saying that I was very pleased with the team performance.
"There were 10 guys out there making their Champions League debut against a very experienced Champions League side so I am very proud of them."
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