I have been known to frequent a local dog park. Any time I enter a park I take a read on the people and temperament (and of course size) of the dogs in the area. I think this is especially important if I haven't encountered the dogs before. Some of it may be my own comfort level but I believe different types of dogs play differently and for that reason the play of one dog can be misread as aggression by another.
Sunday we came across a 18 month old boxer who was friendly but playful. I opted to put Kassa in the adjacent area so that they could run the adjoining fence together. Later a friendly pit bull joined the boxer and so we had the opportunity to watch them play. They had a blast. It was a constant back and forth friendly wrestling match. They were on each others backs, rolling each other over and pinning each other down. Their mouths were always opened in a friendly "I could bite you but I wont" kind of method. They reminded me a lot of bear cubs, both in physical stature and in play.
Kassa doesn't really seem to play that way. He and his other hound buddies remind me more of horses when they play. They are almost always upright (unless they are tired and too wiped out to play). They don't really climb on each other. (A greyhound is more likely to get its skin torn in a wrestling match). They gallop and trot together and will chase a ball. When they get a bit rowdy they may nip at each others necks as they chase each other around.
Because of these differences I think greyhounds may think wrestling is aggressive behavior and the smaller but powerful boxer style dogs may react negatively to the chase. It isn't that either of these behaviors is wrong, I just don't believe they mix well at a dog park.
So in conclusion: Boxers are bear cubs and greyhounds are horses.