Sergio Aguero
Aguero faces a further spell out through injury.

Manchester City season threatens to unravel after defeat to Barcelona in the Champions League was accompanied by injury to top scorer Sergio Aguero, who continues to be hampered by a hamstring problem.

Aguero was replaced at half-time by Edin Dzeko after a recurrence of a hamstring problem which has blighted his season.

Despite scoring 30 goals in all competitions for City, Aguero has already missed significant parts of the campaign with hamstring problems picked up in both December and late January.

The 25 year old made his most recent return in the Capital One Cup Final against Sunderland but having started in the FA Cup loss to Wigan Athletic and at the Nou Camp, faces a further spell on the sidelines at a crucial phase of the term.

"Agüero had the injury and but for that, he would have played in the second half," said City assistant manager Rubén Cousillas. "Hopefully it is nothing serious, but he felt some kind of pain in his muscle.

"Taking him off was more a precaution, but we are doing some tests to assess it. It will be up to the medical staff who determine the extent of the injury, so we cannot speculate about this."

Aguero missed exactly a month after picking up the original hamstring injury against Arsenal in the Premier League last December but returned a month later scoring seven goals in five games before being replaced against Tottenham in January.

Despite missing the whole of February Aguero returned for the League Cup final win over Sunderland but was ineffectual throughout, before starting the Champions League last 16 second leg against Barca.

The ex-Atletico Madrid striker was again a peripheral figure in the first half in Barcelona and was taken off at the break and a further absence could damage City's hopes of winning the Premier League title.

Though Manuel Pellegrini's side trail leaders Chelsea by seven points they have three games in hands over the Blues and can close the gap with victory over Hull City on Saturday before facing Manchester United and Arsenal during the remainder of March.