I got this to work by adding $post_id to the get_field() function. And I needed to get the slug from the category object and not the name:
$sport = get_the_category();
$cat = $sport[0]->name;
$away_team = get_field('away_team_2',$post_id)->ID;
$home_team = get_field('home_team_2',$post_id)->ID;