LONDON (AFP) - Manchester City striker Sergio Aguero is likely to be sidelined for two weeks after suffering a hamstring injury in the champions' 3-0 win against Stoke on Tuesday.

Aguero was forced to come off moments after scoring a penalty in the 74th minute to put Roberto Mancini's side three goals ahead at Eastlands.

City won't know the extent of the Argentina international's injury until Thursday, but assistant manager David Platt has already ruled Aguero out of the FA Cup third round tie against Watford on Saturday.

Aguero, who was City's top scorer last season and netted the goal that won them the Premier League title, is also doubtful for the crucial league clash at Arsenal on Jan 13.

"It is difficult to assess an injury like that, how long it is going to be," Platt said.

"He'll certainly be out on Saturday and in my experience he'd be doubtful for Arsenal. But there are different degrees of hamstring injuries - that's why we need 48 hours.

"It is not just, 'It's a hamstring and this is how long it will be' - we have just got to wait.

"There will be a lot of swelling and a bit of bleeding in there. We don't know how it is going to settle down."

Aguero's absence will be a blow to City, who are currently seven points behind league leaders Manchester United.