Lots of children, perhaps especially boys are not talkative at the age of 11.
Is this a new thing, or has he always been quiet? If it is new, it is probably due to pre-pubescent shyness. If he has always been quiet, then either he isn't very interested in football, or keen on all male company.
Some men don't talk - they just don't see the need. If the rest of the family are talkers, he probably doesn't see the need to say a cheep.
I once taught a pair of twins, the boy said nowt unless forced to speak, his sister had never held her tongue since she learned to speak, so he didn't need to talk!