The striker injured himself in training.
Manchester City FC (@MCFC) March 4, 2013
Many, many fantasy managers were counting on him against the relegation strugglers and the collection "ARGH!" can be heard around the globe.
We await more news on the extent of the injury, but that won't REALLY matter until we learn when Manchester City and Wigan's match gets rescheduled.
UPDATE: More from the man himself.
I felt a crick in my right knee during last training so I won't make it against Aston Villa today— Sergio Aguero (@aguerosergiokun) March 4, 2013
It's a pity I can't be there for my team at this moment. All I can do is recover, and I'm already on it. C'mon, City!— Sergio Aguero (@aguerosergiokun) March 4, 2013