Holders Bayern Munich left Champions League aspirants Manchester City chasing shadows with a 3-1 win on Wednesday to serve notice Pep Guardiola will leave no stone unturned to re-establish their continental dominance.
Franck Ribery, Thomas Mueller and Arjen Robben scored as Bayern left shellshocked City chasing shadows for much of a one-sided Group D encounter that ended the Premier League team's five-year unbeaten run at home in Europe.
Cristiano Ronaldo's hot form continued with a double in Real Madrid's 4-0 rout of FC Copenhagen but he was not the only revered striker among the goals with Zlatan Ibrahimovic also netting twice as Paris St Germain brushed aside Benfica 3-0.
Both, though, were outshone by Greece forward Kostas Mitroglou who grabbed a hat-trick in Olympiakos Piraeus's 3-0 romp at Anderlecht.
A dramatic finale in Turin saw Galatasaray, with manager Roberto Mancini taking charge for the first time, snatch a 2-2 draw with Juventus thanks to Umut Bulut's late goal.
Brazil forward Taison's 76th-minute strike earned Shakhtar Donetsk a 1-1 draw at home to Manchester United after the visitors had led through Danny Welbeck.
Veteran United midfielder Ryan Giggs set a Champions League record by making his 145th appearance, including qualifiers, to surpass former Spain and Real Madrid striker Raul.
Slick Bayern set the standard last season under former coach Jupp Heynckes and a dominant display at the Etihad, to make it two wins from two in Group D, left City under no illusions as to the level they must attain to challenge the continent's elite.
Ribery caught out Joe Hart at the near post to give Bayern a seventh-minute lead and poor defending allowed Mueller all the time he needed to round the City keeper to make it 2-0.
When Robben lashed in a third after 59 minutes City were on their knees but Bayern eased off, Alvaro Negredo pulling one back before the visitors ended with 10 men after Jerome Boateng's late red card.
Shellshocked City manager Manuel Pellegrini told reporters his side had "played very badly".
"It was an important game to see what level we are playing at so we must revise a lot of things," added the Spaniard, tasked with getting City out of the group stage at the very least after two successive failures in the last two seasons.
Ronaldo followed up his hat-trick in Real's 6-1 rout of Galatasaray in their opening Group B fixture with another two against Copenhagen to take his tally to 55 in the competition and 26 in his last 21 Champions League appearances.
Angel Di Maria also struck twice at the Bernabeu and set up Ronaldo's second to boost manager Carlo Ancelotti after a weekend league defeat at home to city rivals Atletico.
Paris St Germain have taken early control of Group C, their game against Benfica wrapped up by halftime at the Parc des Princes.
Ibrahimovic tapped home from close range early on for wealthy PSG, defender Marquinhos added a second goal and the Sweden striker headed home a third from Thiago Motta's corner.
Juventus, who trailed to Didier Drogba's first-half goal for Galatasaray, turned their Group B match around after Fabio Quagliarella's introduction from the bench.
He won a penalty which Arturo Vidal slotted in to level after 78 minutes before the substitute headed in Andrea Pirlo's cross three minutes from time.
Juve fans had barely finished celebrating, however, when Drogba outjumped the defence to head the ball into the path of substitute Bulut who made no mistake.
"That's football," said Juve coach Antonio Conte. "It will be a long and uphill battle but we mustn't get discouraged."
Manchester United manager David Moyes was pleased to take a point in Donetsk which left the former European champions and Shakhtar both on four points in Group A.
Wayne Rooney was forced to watch from the stands after picking up a shin injury in training but fellow England striker Welbeck made up for his absence with a poacher's finish to give United, enduring their worst start to a domestic season for 24 years, an early advantage.
Shakhtar sporadically threatened in a largely lacklustre clash but got the break they needed when a stray Nemanja Vidic clearance fell to Taison who gave keeper David de Gea no chance from six metres.
"They've got a great record against English teams, Shakhtar, so I thought the team stood up well to it tonight," Moyes said.
Bayer Leverkusen left it late to pick up their first win in Group A, substitute Jens Hegeler curling in a free kick in stoppage time to seal a 2-1 home victory over Real Sociedad.
The German side led through a powerful Simon Rolfes header late in the first half before Carlos Vela levelled soon after the break, tucking home the rebound after his own penalty had been saved by Bernd Leno.
Earlier, CSKA Moscow secured their first points in Group D with a 3-2 home triumph over Viktoria Plzen who have lost their first two games.