Otavio, who Pat Nevin was raving about earlier, was replaced at half-time. Jesus Corona takes his place for Porto. Injury or tactical reshuffle? We're not sure.

Adam: Liverpool did face Man City recently in the Premier League and remain the only team to have beaten them this season. Why should they worry about anyone else when on this form? Envy is a fine thing.

Paan: I pray that no one poaches Salah from us for another season. Liverpool can take big strides with him.

Gordon: More than anywhere, a defence needs unity to develop a cohesive partnership. Italians know this, apparently Klopp knows better. Lovren's burned more bridges than the Vikings

We go again in Spain. No changes for either side.

Under way again.

PSG players have already come out.

Marcelo, still holding his arm, counts the amount of Real Madrid players in the tunnel but someone's missing. It's captain Sergio Ramos, but he's here now so they come out.

Andy W: As entertaining as the football is some of me would like to see some decent defending and goalkeeping. Bould, Adams, Seaman, Baresi and Maldini will all be hiding behind the sofa tonight.

Ash: There's still another 135 minutes of this round left guys. Job only a quarter done so far and we've been known to throw games away in ten mins.

Mo: A lot of debate on Liverpool and whether we'll beat the elite teams but any positive result in the Champions League is a great achievement. People questioning the ability but we've already beat City in the League. Let's hope we can hold on second half, expert performance so far.

Cristiano Ronaldo has now scored 10 or more goals in seven consecutive Champions League campaigns, while no other player has done so in more than two.

One of the all-time greats?

(Yes)

Stephen Warnock
Ex-Liverpool defender on BBC Radio 5 Live

Liverpool have been brilliant going forward, good into their rhythm, but Porto have been poor. We were talking about the Champions League and the quality of the sides in there but Porto look poor.

Even Liverpool’s first goal came from a Porto mistake, and that gave them impetus. Porto sat in early and to try and make it difficult for Liverpool. I wonder if that was their game plan, which has gone out the window. Second half could be a long one for them.

Just seen a replay of Real's penalty and the ball slightly bounced up in the air before Cristiano Ronaldo took it. Technically a half-volley.

Anon: Porto would struggle in League Two. Can't believe that bloke is a professional goal keeper.

James: It's only 24 hours since the Spurs comeback and people are already thinking Liverpool have the tie won. Sevilla? Short memories?

Francis: Porto v Liverpool 0-2 at half-time. Is it all over? Ah you're new to covering Liverpool then?

PSG right-back Dani Alves had to go in goal for the final seconds of a recent cup tie.

If a bit of you doesn't want that to happen tonight, then we can never be friends.

Image source, .

Anon: Nobody in Europe can get near Liverpool? So how come they trail Man City by 18 points?

Tom: Porto and Real Madrid could have done with Casillas in goal tonight!

Dan: Let's not pretend that Casillas has been free of blunders in recent years. He's on the bench for good reason. A legend, but has been in steady decline for years.

Pat Nevin
BBC Radio 5 live at Estadio do Dragao

I've seen Liverpool a lot this season and when they play well they are a joy to watch.

There’s been a good intelligence about their play. Like two boxers they sized up each other. After 15 minutes they realised ‘we’re stronger, we’re better, we’ll take this’ And they did, took the game by the scruff of the neck, scored two goals, and if they keep going they can wrap up the tie in the second half.

Image source, BBC Sport

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Alex: English boy, studying at Liverpool University, but supporting FC Porto. This is painful.

Aaron: You can tell Porto aren't used to being challenged domestically, especially at home. Liverpool must wonder if they're replaying Southampton, it's been that simple

Nikhil: Dear Liverpool fans, agreed that your team is in a wonderful form, but hold your horses until you face the likes of PSG, Barcelona, Man City and Bayern Munich.

Cristiano Ronaldo is the first player in Champions League history to score 100 goals for the same club.

That's goal number 115 including Manchester United, extending his own record.

All this talk of him being in decline, but that's his 10th goal in seven Champions League games this season - scoring in every match.

I really do love the Champions League knockout stages.

Moments before that penalty, Raphael Varane shot wide from 30 yards and Karim Benzema had a shot well saved from the edge of the box.

That save led to the corner, which resulted in the penalty.