Juventus might be suffering in the Serie A, but they remain a force to be reckoned with in the Champions League, and they showed why with an impressive win over Manchester City, while Louis Van Gaal and Manchester United were jolted on their return to Europe's premier competition by PSV Eindhoven.

Cristiano Ronaldo, coming off scoring five goals against Espanyol in the La Liga on Saturday, added a hat-trick to open his Champions League campaign as Real Madrid cruised past Shakhtar Donetsk, but the opening night will be remembered for the losses of the two Manchester clubs, both of whom threw away leads.

The first half of the match at the Etihad was pretty disappointing really, with both teams cancelling each other out, as the likes of Yaya Toure, David Silva and Paul Pogba failed to dominate their respective midfields.

There were decent moments here and there, for both sides, with Pogba actually putting the ball in the back of the net from close range, however, the goal was ruled out for offside. It wasn't Pogba who was offside, though, but his teammate Alvaro Morata, who crept past City's backline too early, before missing the right-wing cross from Juan Cuadrado. Pogba would tap the ball in from the far post, but Morata was, rightly, deemed to have interfered with play.

At the other end, Raheem Sterling came the closest to breaking the deadlock, after some good work from Fernandinho put the former Liverpool man through on goal with just Gianluigi Buffon to beat. But then, beating Buffon isn't an easy proposition is it, and the experienced goalkeeper made a smart save to keep the scoreline at 0-0.

Fernandinho was Manchester City's brightest player in that first half, and the midfielder came close as well, with his rasping drive from 22 yards just flying wide of goal, with Buffon beaten.

It did not take Manchester City too long in the second half to score, even if it came in controversial circumstances. A corner from David Silva had Vincent Kompany seemingly climb above Giorgio Chiellini to fire home a header, with replays showing the Manchester City captain clearly using his arms to jump over the Juventus defender and the ball actually coming off the head of Chiellini.

It was a clear foul and a goal that should not have stood, but City didn't care and they nearly made it 2-0 soon after as well, with Buffon making a brilliant double save off Sterling and Silva.

However, Juventus would find parity on 70 minutes as Mario Mandzukic, anonymous until then, slotted home off the inside off the post, after latching onto a nice pass from Pogba.

City's balloon was deflated a little bit more five minutes later as their skipper Kompany, who had forced in that own goal off Chiellini, was forced off the field with an injury, with Nicolas Otamendi given his Champions League debut for Manchester City.

And that balloon went completely bust on 81 minutes as Alvaro Morata scored an absolute peach, curling one with his left foot to leave Joe Hart with absolutely no chance.

In the other Group D game, Sevilla eased past Borussia Monchengladbach, with strikes from Kevin Gameiro, who also missed a penalty, Ever Banega and a Yann Sommer own goal.

At the Bernabeu, Real Madrid did what they had to do, even if they were given some help by Shakhtar Donetsk, who went down to 10 men as Taras Stepanenko saw red for two not-too-smart challenges. The opening goal came via a massive mistake from the visiting team's goalkeeper Andriy Pyatov, who spilled a harmless ball from Isco to allow Karim Benzema to place the ball into an empty net.

Two penalties from Cristiano Ronaldo in eight second half minutes, followed by a late header from the superstar, and it was job done for Real Madrid, even if the win came at a cost, with Gareth Bale taken off in the first half with a possibly serious injury.

In Eindhoven, there was an unfortunate injury as well, as Luke Shaw had to be stretchered off after coming under the challenge of Hector Moreno, who was lucky to escape a red card as well as giving away a penalty. Manchester United later confirmed the left-back had suffered a double leg fracture, which could keep him out for six months.

It took a while for the players to get back into their groove after that seemingly serious injury, which stopped the game for nearly nine minutes, but once it did, there was plenty of goalmouth action.

The opening goal was, expectedly, scored by Memphis Depay, the man who made his move from PSV to Manchester United in the summer. It was a wonderful individual goal as well, with Memphis leaving both Santiago Arias and Jeffrey Bruma for dead, before finishing with aplomb.

Anthony Martial, given his first Manchester United start, owing to Wayne Rooney's injury and Marouane Fellaini's illness, and Ashley Young came close as well, but it was PSV who found the second goal of the game, with Moreno rising high to head home off a deflection from Daley Blind.

As if that wasn't enough, PSV found the winner on 57 minutes courtesy Luciano Narsingh. A brilliant pass from Andres Guardado found Maxime Lestienne on the left, with the winger firing in a perfect cross for Narsingh to head beyond David De Gea from close range.

At the Parc de Princes, it was job done for Paris Saint-Germain, with former Manchester United man Angel Di Maria, showing what Van Gaal is missing with a brilliant strike, while Edinson Cavani scored as well to give PSG a 2-0 win over Zlatan Ibrahimovic's old club Malmo.

Results: Group A: Real Madrid 4-0 Shakhtar Donetsk; PSG 2-0 Malmo.

Group B: PSV Eindhoven 2-1 Manchester United; Wolfsburg 1-0 CSKA Moscow.

Group C: Galatasaray 0-2 Atletico Madrid; Benfica 2-0 Astana.

Group D: Manchester City 1-2 Juventus; Sevilla 3-0 Borussia Monchengladbach.