Goals by Lionel Messi and Dani Alves saw Barcelona take control of their Champions League last 16 tie against Manchester City with a 2-0 win in Tuesday's first leg.

Knockout-phase debutants City matched Barcelona in the first half at the Etihad Stadium, but the game changed early in the second period when Martin Demichelis was sent off following a last-man foul on Messi. The Argentine scored from the ensuing penalty in the 54th minute, taking his tally of goals in this season's competition to seven.

Despite being a man down, City continued to threaten, but in the final minute Alves ran through to score, leaving Barcelona firmly in the driving seat ahead of the return leg on March 12. While Neymar started on the bench for Barcelona after his recent return from injury, City manager Manuel Pellegrini deployed a pragmatic 4-4-1-1 formation, with Alvaro Negredo playing as a lone striker.

Both managers had emphasized the importance of possession before the game and in that domain the visitors quickly stamped their authority, immediately trading passes with their usual hypnotic fluidity. There was no penetration to their passing, however, and when City began to probe, they found fissures in the Barca defense.

A pass from David Silva freed Negredo, who eluded Gerard Pique before lifting the ball over Victor Valdes from a tight angle, but there were no City players up in support. Barca goalkeeper Valdes was then given a moment of discomfort when Vincent Kompany got his head to a free-kick from Silva, sparking a goalmouth scramble that was cut short when Negredo was penalized for an infringement.

Negredo hit a snapshot straight at Valdes, before Barca came to life, with Messi firing over from the edge of the box and Xavi extending City goalkeeper Joe Hart with a rasping 25-yard drive. It was an encouraging first half for the home side, but eight minutes into the second period the balance of the tie suddenly shifted in Barcelona's favor.

Andres Iniesta's pass put Messi through on goal and Demichelis, sliding in from behind, brought the Argentine down. The offense occurred right on the edge of the box, but referee Jonas Eriksson awarded a penalty and after Demichelis had trudged off, Messi planted the spot-kick past Hart.

Pellegrini sent on Joleon Lescott and Samir Nasri in place of Aleksandar Kolarov and Jesus Navas, and Nasri quickly had a sight of goal, only for Pique to block. Alves teed up Xavi to shoot over and then drilled narrowly wide after a one-two with Alexis Sanchez as Barca threatened to twist the knife, while Neymar's introduction seemed to presage further bad news for City.

Instead, the hosts continued to push, with Valdes plunging to his right to repel a volley from Silva in the 77th minute. Barca had the final say, however, with Alves gathering a pass from Neymar and tucking the ball between Hart's legs in the final minute to further tighten the Catalans' grip on the tie.

Manuel Pellegrini is normally a serene, calm individual that isn't known for post match tirades. But that is no longer the case after the Chilean manager lashed into referee Jonas Eriksson following Manchester City's 2-0 loss to Barcelona in their Champions League Round of 16 first leg tie. 

You would have thought the spirit of Jose Mourinho hijacked Pellegrini's body in the press conference, as the former Malaga manager felt that Eriksson, who is from Sweden, was not prepared to officiate a match at the highest level. He also accused Eriksson of his decisions giving Barcelona the victory, which included point to the sport for Lionel Messi's penalty after giving a red card to Martin Demichelis for the center-back fouling his Argentine teammate in the 53rd minute. 

"The referee decided the game," Pellegrini said. "From the beginning I felt the referee was not impartial to both teams. He did not have any control of the game. I think it was not a good idea to put a referee from Sweden in such an important match."

Pellegreni did eventually turn to discussing his side's own play that sees Manchester City having to at least score two times at the Nou Camp in three weeks time or be knocked out of the competition.  

"You cannot make mistakes like we did against a great team like them," he said. "It will always be costly. We will try our best at the Nou Camp but the second goal makes it very difficult. We will see what we can do. We try to win every match in every competition and that will not change in the second leg." 

Pellegrini's opposite half, Barcelona manager Tata Martino, was in obviously different spirits after his side quelled any talk of the club's decline. 

"For ten minutes during the first half we lost control a little but in the rest of the game we did well," Martino said. "We have to remain calm and continue along the same path because there is no time to relax as we must now start thinking about our next game in Liga. We have clear objectives in each tournament. We can play better or we can play worse than tonight but in no way are we going to relax." 

Martino also praised his top star Lionel Messi for not only causing the defining moment of the match, but for his overall diligent performance."To avoid repeating myself, I'll say that what impressed me today from Messi was his workrate when the ball needed winning back."

Manchester City's new signing Martin Demichelis will be out for up to six weeks with a knee injury, the Premier League club announced on Friday.

The 32-year-old Argentine center-back only arrived from Atlético Madrid on Sunday.

After injuring himself in training, he underwent a scan that revealed ligament damage, but a statement on the City website said that surgery would not be necessary.

"A knee injury sustained in training is set to keep new arrival Martin Demichelis out for around six weeks," read the statement on www.mcfc.co.uk.

"The club doctor confirmed a scan last night (Thursday) revealed ligament damage, but that surgery is not required."

Demichelis's absence adds to manager Manuel Pellegrini's problems in defense, with captain Vincent Kompany currently sidelined by a groin problem and Micah Richards unavailable due to a hamstring complaint.