Lazio defender Stefan de Vrij blocks Alessandro Florenzi's shot and gets injured. He's OK to continue after treatment.

Here comes another Lazio change. Patric replaces Stefan Radu at the back. And now Jordan Lukaku wins a corner.

The entire feel around this game has changed now. Roma looked comfortable but Lazio are pushing for an equaliser.

Immediately after the goal, Roma brought on Gerson for Stephan El Shaarawy.

Kostas Manolas chests Nani's cross just out of play for a corner, but it hit his arm. It looked accidental but that doesn't seem to matter as much these days. The referee says corner...

Well now.

He's gone to the video referee and after some deliberation, changes his mind. PENALTY.

Aleksandar Kolarov, who has had a good game for Roma, shoots from outside the box but keeper Thomas Strakosha holds it.

Lazio are starting to create more attacking moves, but Roma's defence are holding firm.

Meanwhile, Roma's Radja Nainggolan hatchets Stefan Radu and is booked.

A beautiful passing move by Roma ends up with Radja Nainggolan 20 yards out but his shot lacks the venom or precision of his opener and it's held by the Lazio keeper.

Brave man as Nani brings down Roma captain Daniele de Rossi with a late tackle. The Lazio substitute is booked.

Lazio have conceded nine goals in the opening 15 minutes of the second half, at least three more than any other side in Serie A this season.

Jordan Lukaku replaces captain Senad Lulic and winger Nani is on for midfielder Lucas Leiva. That is not a like for like change...

What on earth happened to Lazio at the break? Aleksandar Kolarov's cross is almost turned into his own net by Lucas Leiva. The light blues are getting some subs ready.

Lazio are starting to lose their heads now. Kostas Manolas was injured in the first half and he's down again. He was caught late by Luis Alberto, who has been rightly booked. The Greek's sock is torn in half.

This result would take Roma from fifth to third - above Lazio. A long way to go though.

Bastos brings down Aleksandar Kolarov with a sliding tackle. Penalty.

The second half has started.

Here was what Roma legend Francesco Totti, who retired in the summer and is now a club director, had to say before kick-off.

"Today will definitely be a new feeling: my first derby observing after so many on the pitch. But my love for this team will never change. I hope today's derby is a great example of sport, my sport: the most beautiful, the one I have always loved and will never stop loving!"

Barca have just conceded four goals in La Liga this season, the fewest they have ever let in after 12 games.

Level at the break.