given that tennis apparently has been the only common denominator, it seems to me that you've been activity partners more than friends. if anything, you've been more competitors against each other than actually engaged in activities that facilitate the building of friendships. i submit that tennis buddy would be a more appropriate categorization of the relationship you've had with this person. if you wish to keep a relationship going with this person, you are probably best served by choosing activities that provide a similar set of dynamics. but you may find that none of your current interests are a good fit for this other person. it happens; things and people change. you may find this to be true even within the dance world. while i started in ballroom, i danced salsa almost exclusively for a number of years. i tired of salsa, and nowadays i rarely see any of the people i used to know from the salsa scene.