Cristiano...

A familiar face for Liverpool fans. On comes Marko Grujic for Porto. Striker Toni Martínez is off. A change in shape it seems.

Back under way in Porto. More goals to come?

Sylvain Distin
Former Manchester City defender Sylvain Distin on BBC Radio 5 Live

If we see that Kevin de Bruyne tackle in the Premier League it's a red - as much as I wouldn't want to see him off the pitch. Whether he means to or not doesn't matter.

But it's the Champions League and the referees are sometimes different. I'm happy the referee didn't have a proper look at it because I don't think we would still be seeing De Bruyne on the pitch.

Prince Gyimah: Those asking why KDB is still on the pitch, the answer is very obvious. This is the Champions League. Unlike the Premier League, the officiating standards is better. That can be seen with the flags raised quicker for offside. Second, there's less VAR involvement.

Mandy Smith: Fifty-fifty tackle by de Bruyne with no obvious mal intent. Anyone fair-minded can see it deserved at most yellow.

Penny for Pep's thoughts?

Paris St-Germain are unbeaten in 40 of their past 41 Champions League matches in which they were leading at half-time (W37, D3, L1), but the only loss in this run came against Manchester City in last season's semi-finals (2-1 loss after 1-0 lead).

Image source, Getty Images

Real Madrid 0-1 Sheriff Tiraspol 👀

Sylvain Distin
Former Manchester City defender Sylvain Distin on BBC Radio 5 Live

We were expecting City to dominate the ball and PSG to be happy to sit back and hit them on the counter. In the first 20 minutes City were slow in the final third, they kept the ball but didn't create many chances. In the last 15-20 minutes something changed and they were a lot more dangerous but they didn't manage that last pass or there was always someone there to block the shot.

It's a shame we didn't see more goals. A slow start from City but you have to give credit to PSG for their defence.

Gift-wrapped.

Image source, Getty Images

Image source, Getty Images

Michael Brown
Former Man City midfielder on BBC Radio 5 Live

A special first half of quality from both teams - we've seen flashes of brilliance. Ultimately City left that bit of space and someone we weren't expecting in Idrissa Gueye was able to score that wonderful goal into the top right corner. How City didn't equalise, hitting the bar twice, I'm not sure.

But it's been a great first half.

Is there a huge shock in the making at the Bernabeu?

At half-time, it certainly looks that way as Moldovan champions Sheriff Tiraspol lead Real Madrid 1-0. This is just Sheriff's second Champions League game proper, having come through four rounds of qualifying this season.

Meanwhile, 10-man AC Milan lead Atletico Madrid 1-0, Borussia Dortmund are 1-0 up against Sporting Lisbon and Club Bruges have battled back to lead RB Leipzig 2-1.

Idrissa Gueye's goal the difference.

Noodles: Another Champions League tournament, another season of watching PSG players mobbing the ref at any given opportunity. Is anyone ever going to anything about it?

Liverpool are cruising.

Yep, no idea how it wasn't a red card for KdB.

WordEngineer: How's that tackle by De Bruyne not a red card and the one made by Wan Bissaka 2 weeks ago one?

VN CA: How is KDB still on? Remember the red card to Wan-Bissaka? Where is the consistency? Shambles

A huge turnaround, this.

Mats Rits forces the ball home after a few scrappy attempts saw the it bobble into his path just a few yards out.

From one angle this looks like being a spectacular own goal from Achraf Hakimi, diving in full stretch to get his head on Riyad Mahrez's cross and almost planting it into the roof of his own net.

In the end, it turns out to be a superb interception.

Three minutes to half time and City almost restore parity.

Ruben Dias wriggles free at the far post from Jack Grealish's corner but his header is batter out by Gianluigi Donnarumma.