What you need to know:
- Paris Saint-Germain brought in Lionel Messi hoping that the Argentinian great would be the final piece of the jigsaw as they bid to finally land the Champions League title
Cristiano Ronaldo rescued Manchester United again, while Lionel Messi scored twice for Paris Saint-Germain and Liverpool beat Atletico Madrid in the Champions League this week.
Here, AFP Sport takes a look at five talking points from a dramatic round of matches:
Messi still reigns supreme in Europe
-- Paris Saint-Germain brought in Lionel Messi hoping that the Argentinian great would be the final piece of the jigsaw as they bid to finally land the Champions League title.
He is yet to score in Ligue 1, but has so far done what he was signed to do by netting three times in as many games in Europe.
The six-time Ballon d'Or winner stepped up when PSG were trailing RB Leipzig in Paris, netting twice, including a Panenka penalty, to rescue a vital 3-2 win.
Ronaldo pulls off another Man Utd escape act
-- For the second time in as many games in Europe, Manchester United had Ronaldo to thank for another come-from-behind victory at Old Trafford.
Ole Gunnar Solskjaer retains the backing of the United hierarchy, but his team produced another topsy-turvy display as they fell two goals down to Atalanta inside the first 30 minutes.
Crucially, United struck early in the second half via Marcus Rashford, taking advantage of a porous Atalanta defence to level through captain Harry Maguire before Ronaldo soared to power in the winning header.
Plenty of concerns remain about the defence and general cohesion, but United's attack is a considerable point of strength -- with Ronaldo again coming to the rescue.
Favourites Bayern, Man City in ominous form
-- Bayern Munich producing a scintillating four-goal burst in 15 minutes that blew away Benfica in Lisbon, while Pep Guardiola described Manchester City's 5-1 rout of Club Brugge as one of their "best performances in Europe".
Six-time champions Bayern overcame key absences -- including that of unwell coach Julian Nagelsmann -- to make it three wins from three, with 12 goals scored and none conceded.
An untimely injury to Robert Lewandowski derailed Bayern's title defence last season, when they exited on away goals to PSG in the quarter-finals. While the Poland star is back doing what he does best, the return to form of Leroy Sane has boosted Bayern even more.
As for City, who lack an out-and-out striker after being rebuffed in their pursuit of Harry Kane, Phil Foden showed he is more than capable of leading the attack as a false nine. His outstanding display in Bruges helped City overpower a side that had drawn with PSG and then beaten RB Leipzig in Germany.
Atletico continue run of Spanish woe
-- Diego Simeone led Atletico to a memorable La Liga title last season but Spanish clubs appear to not be the forces they were in recent years.
His side are in danger of missing out on a last-16 place for only the second time in nine seasons after a dramatic 3-2 home loss to Liverpool, while Barcelona are struggling in their group and Real Madrid lost at home to minnows Sheriff Tiraspol last month.
Atletico, losing finalists in all-Madrid finals in 2014 and 2016, are second in Group B but level on points with third-placed Porto and have to visit Anfield next time out.
Ten Hag's Ajax dark horses again
-- Dutch champions Ajax raised hopes they could at least replicate their surprise run to the 2018-19 semi-finals with an impressive 4-0 dismantling of Borussia Dortmund in Amsterdam.
Erik ten Hag has successfully rebuilt his side after a series of high-profile departures to Europe's richest clubs in the last two years, including Frenkie de Jong, Matthijs de Ligt, Hakim Ziyech and Donny van de Beek.
But his new crop have won three of three group stage matches.
Brazilian winger Antony, 21, will have alerted scouts to his ability after capping a brilliant individual display with a wonderful goal. Sebastien Haller has proven a clever buy from West Ham and is the Champions League top-scorer this term with six goals.