Champions League holders Bayern Munich extended their record run to 12 straight wins in the competition as they thumped Atletico Madrid.
Just 59 days after lifting the 2020 title in Lisbon, Hansi Flick's side were in ominous form again as they made light work of Diego Simeone's usually watertight side.
Winger Kingsley Coman, matchwinner against Paris St-Germain in Lisbon at the end of August, scored in either half of a superb all-round display.
Midfielders Leon Goretzka and Corentin Tolisso also found the back of the net in a near-faultless performance from the German giants.
Only Real Madrid and AC Milan have retained the European Cup since Brian Clough's Nottingham Forest managed the feat in 1980, but few would back against a Bayern repeat this time around.
Bayern were already favourites with the bookmakers before this warning sign, which saw the holders rain in 16 efforts on goal.
Coman opened the scoring when he deftly collected a Joshua Kimmich pass to fire across goal and the France winger then found Goretzka who doubled the lead with an angled drive.
Atleti had an early response in the second half ruled out for offside and Tolisso wrapped up victory with a fantastic swerving shot from 25 yards.
Bayern scored a club record 43 goals in last year's campaign and made it four for this run when Coman ran on to Thomas Muller's clever pass to sprint clear from the halfway line and find the far corner.
Over in Spain, thirteen-time European Cup winners Real Madrid were handed a humiliating defeat as a shambolic first-half performance was clinically punished by a second-string Shakhtar Donetsk side.
The Ukrainian champions arrived in Madrid without 13 first-team players after 19 positive Covid-19 tests throughout the club left them needing to call up youth-team players.
But Luis Castro's young side were undaunted and swept into an amazing, but thoroughly warranted, 3-0 lead at Real's empty Alfredo di Stefano training ground.
Goals from Luka Modric and Vinicius Junior after the break gave Real hope, but there was no escape for the competition's most decorated side despite a dramatic finale.
Federico Valverde thought he had hit a stoppage-time leveller but after a check at the pitchside monitor referee Srdjan Jovanovic disallowed the goal for offside.
Club legend Zinedine Zidane won the Champions League in each of his first three seasons in charge of Real, but his decision to rest players with next Saturday's El Clasico against Barcelona in mind was a rare, and huge, aberration.
Without captain Sergio Ramos - left in the stands with a knee injury - Real's defence was a mess and could do little to prevent Mateus Tete and Manor Solomon scoring either side of a Raphael Varane own goal.
Tellingly, Real have now lost seven of their last eight Champions League games without Ramos at the heart of their backline.
Former Tottenham midfielder Modric hit a stunning long-range strike to bring a ray of hope and, although Vinicius scored within 15 seconds of coming, on Shakhtar held on for a famous result.
RB Salzburg 2-2 Lokomotive Moscow
Real Madrid 2-3 Shakhtar Donetsk
Bayern Munich 4-0 Ateletico Madrid
Inter Milan 2-2 B. Monchengladbach
Man City 3-1 FC Porto
Olymiakos 1-0 Marseille
Ajax 0-1 Liverpool
FC Midtylland 0-4 Atalanta