I didn't know there were so many tennis courts in Melbourne. I did a check of an area of greater Melbourne out to Ballarat for access 
TOTAL': 6788
EMPTY: 5213
PRIVATE' 1575
So you could extract all blank access tags and perform an automated change to private where the title does not include  the word Club or Public or run a map roulette. You could also narrow it down further if there is only a single court..

The good news is most of this area is private but it's not an easy fix overall and will require local knowledge of tennis.clubs. LEt me know your thoughts.