Forlan picked up a thigh strain while on international duty and each test has shown a worse picture than the one before.
"The medic told me I should recover in the next two months," he told Radio 1010.
"I have had injuries in my career, but this is the worst. None had hit me this hard before.
"I don't think I injured myself with the way I kicked the ball, but rather I must've dragged my ankle.
"Between club ties, internationals, the World Cup and Copa America, I haven't really stopped for a year and a half. I imagine that, and all the travelling that goes with it, had a real influence."