Manchester City were dealt a blow after new signing Martin Demichelis was ruled out for up to six weeks.

The Argentine international damaged knee ligaments in training, leaving Manuel Pellegrini again with a couple of headaches in the central defensive department, although the defender will not require surgery.

Demichelis was brought in to act as cover for the injured Vincent Kompany, while Matija Nastasic has only just returned from injury.

Meanwhile, Manchester City striker Sergio Aguero has praised Manuel Pellegrini for the manner in which he has united the squad this season.

City have not had the best of starts, losing to newly-promoted Cardiff, but Aguero believes the feeling within the squad is much better than it was under former manager Roberto Mancini.

"Every manager is different, but the whole squad has really been enjoying his training sessions and he's made time to speak to every player," Aguero told Match of the Day Magazine.

"It's not just Manuel Pellegrini's arrival, the new signings have bonded really well.

"I hope to score a lot of goals this season to win back the Premier League. Obviously my job is to score and create goals, but the team result is the most important things so I'm happy as long as we're winning games."

Aguero believes Manchester United and Chelsea will be their biggest threats to the English Premier League title.

"Man United will be desperate to retain it under their new manager (David Moyes) and their squad is impressive," Aguero added.

"Chelsea will also be dangerous, and you know Jose Mourinho will bring out the best in them.

"But we have a new manager too and I think the other teams will be looking at us as potential champions this season."

Manchester City next face Stoke in the Premier League, a week from Saturday.