"I like football"
Translation:Ninapenda mpira wa miguu
The -a is concordant with mpira, not miguu. It's "ball of (the) feet." Netball is mpira wa pete, "ball of (the) ring", and basketball is mpira wa kikapu, "ball of (the) basket".
All of these are ball games -- michezo ya mpira, "games of ball".
Can you see how this works? wa miguu is a modifier to ball, telling us what type of ball we're talking about. Likewise ya mpira tells us what sort of games these are. The important part is first noun, and it's that one's class we take our agreement from.