Last season's runners-up broke a plethora of unwanted records as they fell to a humiliating 7-2 defeat at the hands of Bayern Munich, who scored five times in the second half alone in a ruthless and clinical display in North London.
The drama of that game was arguably matched at Anfield the following night when Liverpool threw away a three-goal lead against Red Bull Salzburg before eventually running out 4-3 winners to pick up their first win since lifting the trophy.
Real Madrid also survived a major scare at home to Club Brugge having found themselves two goals down at half time, although they were forced to settle for a point following their second-half comeback.
Here, Sports Mole selects its Champions League team of the week for matchday two.
A hugely competitive XI, particularly in the forward areas, forces us into a rather unorthodox 3-2-3-2 formation, and the battle for places starts with the gloves. Andre Onana and Guilherme both deserve mentions, but Andriy Pyatov pips them to a place between the sticks largely due to his fine penalty save against Atalanta - a stop which enabled Shakhtar Donetsk to go on and score a last-gasp winner.
Red Star Belgrade also left it late to beat Olympiacos - and even then will perhaps feel fortunate despite their visitors being reduced to 10 men - but Nemanja Milunovic was central to holding the Greek outfit at bay and then popped up with an 87th-minute goal which gave the home side the lead.
Genk were another side to ride their luck at times with the woodwork coming to their rescue on a couple of occasions during an impressive goalless draw against Napoli, but credit must also go to some committed defending - most notably when Carlos Cuesta cleared an effort off the line.
Unsurprisingly following their seven-goal show in North London, Bayern are the best-represented club in this week's team, and their demolition job was started by Joshua Kimmich's stunning strike which, at the time, was only enough to level things up against Spurs.
Philippe Coutinho appears to be enjoying a new lease of life in Munich following a difficult spell at Barcelona and the Brazilian ran the show on Tuesday night. His return of one assist - an impudent flick to Robert Lewandowski - was not as impressive as some of those around him, but his impact on the game was as big as anyone's.
The attacking talents in front of him means that Coutinho has to sit in a slightly deeper role in this team alongside Thomas Partey, who was a driving force in the Atletico midfield throughout their win against Lokomotiv Moscow and also popped up with the goal which made the points safe.
Real Madrid duo Casemiro and Toni Kroos deserve mentions - mainly for their second-half performances - while Marko Marin, Donny van de Beek and Magomed Ozdoev can all consider themselves unfortunate to miss out on a midfield spot too.
There are more honourable mentions needed in the forward positions. Salzburg duo Hwang Hee-Chan and Takumi Minamino would have done enough to make the team in most other weeks, Raheem Sterling changed the game when he came on against Dinamo Zagreb, Achraf Hakimi scored two well-taken goals for Dortmund, Sadio Mane was at the centre of some sparkling football in the first half-hour or so for Liverpool and Hakim Ziyech scored arguably the goal of the round.
Selecting the three behind the strikers is a difficult job, then, but the one position of which there was no doubt was Serge Gnabry's. The former Arsenal man made a storming return to North London with four second-half goals and an assist in Bayern's rout, terrorising Serge Aurier and providing deadly finishes each time he got through.
Alongside him there also needed to be a place for Lionel Messi, who looked like he had not missed a beat on his return from injury. The Argentine maestro's assist for Luis Suarez's second was particularly special, jinking past three defenders before teeing up his striker.
Suarez's return to goalscoring form in the Champions League was a timely one for Barcelona as they came from behind to beat Inter, and both of his goals were brilliantly taken too - the first a crisp first-time volley from the edge of the box and the second a lovely touch and finish after Messi's magic.
Mohamed Salah also scored twice in Liverpool's win over Salzburg and, while his first may not have been as eye-catching as some of the stuff the Reds played in the first half, he was nonetheless on hand when his side needed him. The finish for the winning goal, which came after Salzburg's remarkable fightback, was much harder than he made it look.
Up front alongside Suarez is Robert Lewandowski, who showcased exactly why his manager described him as the best striker in world football with a clinical brace against Spurs, producing two finishes of the highest order, including one just before half time which seemed to change the game completely.
It would be remiss not to mention some of the other strikers who were unfortunate to miss out, though, particularly Emmanuel Dennis, who will never forget his unorthodox brace at the Bernabeu. Roberto Firmino, Artem Dzyuba, Sardar Azmoun and Cristiano Ronaldo were all in contention too, but the competition this week was simply too fierce.