Under-fire Jose Mourinho and Manchester United revelled in an incredible smash and grab victory at Juventus, while Real Madrid continue their revival and Cristiano Ronaldo watches on as his magnificent volley counts for nothing.

AFP Sport looks at five things we learned in the Champions League this week:

Under pressure following a series of dismal performances, Manchester United Jose Mourinho pulled off a hugely important 2-1 away victory at Juventus reminiscent of his past as the "Special One" that gives United a huge boost ahead of the Manchester derby at the weekend.

The Portuguese was in his element winning at the home of his former fierce Serie A rivals, charging onto the pitch to taunt the home fans in Turin by cupping his ear as United players and supporters celebrated a win gained by Mourinho's decisions from the bench.

He brought on Juan Mata and Marouane Fellaini with 11 minutes left and United deservedly behind to a Cristiano Ronaldo wonder goal, and both were instrumental in the turnaround, Mata whipping home the equaliser and Fellaini flicking on a cross that Leonardo Bonucci eventually nodded into his own net.

The 55-year-old could do with some more of that golden touch at the weekend.

Having reached two of the last four finals, Juventus looked like genuine challengers for their first Champions League in over two decades when Ronaldo lashed home his 65th-minute volley.

Juve looked set to win Group H with two games to spare when Ronaldo rifled in Leonardo Bonucci's magnificent long pass just at it dropped over his shoulder, giving the Serie A leaders a thoroughly deserved lead.

However despite their impressive winning record Juventus have shown weakness this season. They almost let United back into it at Old Trafford after switching off and this time they were punished for missing gilt-edge chances by a cynical away side.

Juve are still odds on to qualify for the knockout stages but if Massimiliano Allegri is to bring the club their third European Cup he will have to make sure they can keep up their impressive displays for the full 90 minutes.

In a full-blown crisis under previous coach Julen Lopetegui, Real Madrid look a new side under caretaker manager Santiago Solari. The European champions' third win in three matches since Solari took charge was a 5-0 hammering of Viktoria Plzen.

The Czechs were not the strongest opposition but Wednesday night's display was Madrid at their swaggering best.

Real are set to qualify from Group G alongside Roma and a continuing of this form will put the rest of the competition on red alert.

After years in the doldrums Italian clubs other than Juventus are starting to make a mark on the competition and going toe-to-toe again with the world's best.

Napoli, who have mostly failed to transfer their recent domestic revival to the European stage, were unlucky to not have won at least one of their two clashes with megabucks PSG and on Tuesday gave as good as they got in their 1-1 draw with Thomas Tuchel's side.

Inter Milan were dominated by Barcelona and saved from defeat by an inspired performance from goalkeeper Samir Handanovic and a poacher's finish from striker Mauro Icardi, who snatched a late draw that makes Luciano Spalletti's side favourites to qualify ahead of Tottenham Hotspur.

Roma meanwhile are keeping pace with Real Madrid in Group G thanks to a hard-fought 2-1 win at CSKA Moscow, Eusebio Di Francesco's side performing better in Europe than in Serie A.

Crushing everything that moves in Ligue 1, Paris Saint-Germain can't seem to establish themselves as a European powerhouse.

PSG are third in Group C after their battling 1-1 draw with Napoli in the Stadio San Paolo cauldron, and while they are only one point behind leaders Liverpool, Tuchel's side have only managed to beat Red Star Belgrade in four matches.

The French champions' Qatari owners have spent huge sums in order to try to barge their way into the European elite, but have so far failed to convince away from the relative safety of Ligue 1.