Aprilia rs 125 wobly sprocket?

i have jus brought a aprilia rs 125 and when jus havin a general look around the bike i came across the sprocket and when i touched it , it was wobbling side to side i could see bearin kinda things behind it but the sprocket looked like it had no way of it bein holding to the wheel so is it supposed to be wobbly can any1 help please thanks very much