Last years Champions Inter Milan drew 2-2 at competition debutants FC Twente as the Champions League group phase began on Tuesday, while Manchester United were held by Rangers and Barcelona thrashed Panathinaikos.
Theo Janssen was the star for Twente, Dutch champions for the first time in their history last season, scoring one and making one to frustrate Rafael Benitez's side on a rain-soaked night in Enschede, eastern Holland.
While Wesley Sneijder gave the visitors the lead on his return to home soil, but Janssen curled in a stunning free-kick before Diego Milito's own goal gave the hosts the lead, only for Samuel Eto'o vital equaliser earning the Italians a point.
Rafael Benitez, who replaced Jose Mourinho at the Inter helm after moving from Liverpool in the summer, declared himself pleased with his side's Group A opener.
"The first half was very difficult but we did very well in the second," he said. "We controlled the game and I'm satisfied with the second half against a difficult team."
The result leaves Inter and Twente in a four-way tie with Tottenham Hotspur and Werder Bremen, whose game in north-western Germany also ended in a 2-2 stalemate.
Tottenham went 2-0 up inside 20 minutes after a Petri Pasanen own goal and a Peter Crouch header, but the hosts pulled one back through Hugo Almeida and drew level early in the second period when Marko Marin fired in a low drive.
"That first 42 minutes or so was the best you could ever see us play, we passed the ball and opened them up time and time again. But then we conceded a bad goal, which suddenly bought them back into the game." said coach Harry Redknapp.
United made 10 changes for the visit of Rangers and were made to pay as the Scottish champions ground out a goalless draw in their Group C fixture at Old Trafford.
The hosts dominated possession but without testing visiting goalkeeper Allan McGregor, and three long-range drives from Irish midfielder Darron Gibson were all they had to show for their efforts.
The evening ended on a sour note for the 2008 European champions, who had Ecuador international winger Antonio Valencia stretchered off following a sliding challenge from Kirk Broadfoot with a suspected dislocation and fracture to his ankle.
"Rangers set their stall out to defend and play on the counter-attack, and you have to respect that," said United coach Sir Alex Ferguson.
"They came knowing what they wanted to do and they did it well. Our final ball wasn't good enough to get three points."
Current Spanish league leaders Valencia top Group C after a convincing 4-0 win at Champions League new boys Bursaspor of Turkey.
Barcelona began their European campaign in similarly spectacular fashion, smashing five typically well-worked goals past Greek champions Panathinaikos in a 5-1 victory at Camp Nou.
The visitors had the temerity to take a 20th-minute lead through former Lyon forward Sidney Govou, but Barca were 3-1 up at the interval thanks to a Lionel Messi brace that sandwiched a close-range David Villa strike.
Messi spurned the chance to claim a hat-trick when his tame second-half penalty was saved, but goals from Pedro Rodriguez and Dani Alves in the 78th and 93rd minutes added gloss to the scoreline.
"We couldn't win on Saturday and knew we had to win tonight," said Pedro, whose side fell to a shock 2-0 defeat at home to newly promoted Hercules in La Liga at the weekend.
An 87th-minute goal by Dame N'Doye earned FC Copenhagen a 1-0 win at home to Russia's Rubin Kazan in the other group game.
Lyon, semi-finalists last season, and two-time champions Benfica both got off to winning starts in Group B. The French side prevailed 1-0 at home to Schalke, who had centre-back Benedikt Howedes sent off in the first half after Michel Bastos had put Lyon ahead.
Benfica beat Israeli competition debutants Hapoel Tel-Aviv 2-0 in Lisbon, with Brazil centre-back Luisao netting the 5,000th goal in Champions League history.