Martin Demichelis: "I tackled him [Messi] because we were still outside the box. But I don't blame the referee. It happened all too fast.
"I have seen the moment again on TV and think 'why did I have to tackle him and not keep running by his side?'
"I was sure that I would get the ball when I made the tackle. And then you think that you will steal the ball from Messi, you realise that you don't. But I made the foul."
Demichelis will be suspended for the return leg in Catalonia, which takes place on Wednesday March 12.
MAN CITY 0 BARCELONA 2
MAN CITY
1. Joe Hart
5. Pablo Zabaleta
4. Vincent Kompany
26. Martin Demichelis
22. Gael Clichy
15. Jesus Navas 57'
25. Fernandinho
42. Yaya Toure
13. Aleksandar Kolarov 57'
21. David Silva
9. Alvaro Negredo 74'
Subs
30. Costel Pantilimon
2. Micah Richards
6. Joleon Lescott 57'
8. Samir Nasri 57'
10. Edin Dzeko 74'
14. Javi Garcia
35. Stevan Jovetic
BARCELONA
1. Victor Valdes
22. Dani Alves
3. Gerard Pique
14. Javier Mascherano
18. Jordi Alba
6. Xavi
16. Sergio Busquets
4. Cesc Fabregas 86'
9. Alexis Sanchez 73'
10. Lionel Messi
8. Andres Iniesta
Subs
13. Jose Pinto
7. Pedro
11. Neymar 73'
15. Marc Bartra
17. Alex Song
21. Adriano
24. Sergi Roberto 86'
Lionel Messi and Daniel Alves punished 10-man Manchester City in the first leg of the Champions League last-16 tie at the Etihad Stadium.
Four-time World Player of the Year Messi struck from the penalty spot with 54 minutes gone after being brought down by Martin Demichelis, who was sent off.
City had their chances but Barcelona dominated possession throughout and were rewarded when Alves struck the second in the last minute.
City had set up well in an attempt to soak up Barcelona pressure and catch them on the break but the task proved beyond them after Messi punished a mistake early in the second half.
The Argentinian raced away and, although replays suggested contact by Demichelis may have been just outside the box, a straight red card was brandished and the penalty awarded.
The hosts kept on pressing but they failed to make the most of their opportunities and they were picked off again as time ran out.
Barcelona coach Gerard Martino had said the key to victory was possession and so it proved, as the visitors controlled the ball for long spells.
Yet City appeared to have been expecting that having packed midfield.
Fernandinho's return from injury allowed manager Manuel Pellegrini to deploy five across the middle with Alvaro Negredo operating as a lone striker.
After 14 minutes largely on the back foot, but with Barca yet to create a clear-cut chance, Vincent Kompany picked out Negredo with a long ball.
The powerful forward controlled well on the edge of the box but Javier Mascherano, with whom he regularly battled, managed to scramble away.
Negredo caused more trouble in the box after Jesus Navas crossed from the right but Swedish referee Jonas Eriksson penalised him for a foul on goalkeeper Victor Valdes.
Barca had another scare as Valdes was beaten in the air by Kompany at a corner but he scrambled back to gather on the line. Negredo had another chance from outside the area but shot straight at Valdes.
All these chances punctuated spells of prolonged Barca possession and the Catalans did eventually pierce the hard-working back line of Kompany and Demichelis.
Cesc Fabregas played in Andres Iniesta only for Yaya Toure to get back and Messi linked well with Xavi and Iniesta before shooting over.
Joe Hart saved well from a strong Xavi shot and Kompany bundled Messi over.
Negredo had another chance to open the scoring before half-time but glanced a header wide from Navas' cross.
City were to regret those missed chances as Barcelona upped the tempo for the second half.
Messi certainly appeared to move up the gears and did well to release Fabregas down the left.
That attack came to nothing but Messi was clearly in the mood and had the hosts, and particularly, Demichelis in trouble as he burst through on goal.
Demichelis could not keep pace and slid in in a desperate attempt to tackle, but succeeded only in tripping his fellow Argentinian.
Contact appeared to be just outside the area but Eriksson pointed to the spot and gave Demichelis his marching orders.
Messi calmly stroked home the penalty down the centre as Hart dived to left.
Pellegrini sent on Joleon Lescott to reinforce the defence but recognised damage limitation was not an option and also introduced Samir Nasri.
Nasri was soon in the action and had a shot blocked from a Negredo lay-off.
Barca could have taken even greater command of the tie as Xavi shot over and Alves fired across goal.
City broke again but Gael Clichy wasted an opening and a well-struck Silva volley was clutched by Valdes.
The hosts, however, may have had a stroke of luck as Gerard Pique had a late goal ruled out for a marginal offside.
Edin Dzeko had a late chance for City but was harshly penalised for a foul.
There was no reprieve for City in the final minute as Alves got behind the defence and fired past Hart.