You may want to talk to the coach and get his/her help cultivating a buddy for DS. The coach may be able to pair them up at practice consistently and that way it isn't coming from you.
My DD10 had issues with one kid at basketball last year. She always seems to get paired up with that kid at practice -- they played the same position so they played against each other every practice. When I talked to the coach, he saw it as an opportunity to buddy DD up with another kid who didn't know any of the other kids on the team (the rest of the kids had played soccer together). He also switched it around so that my DD played on the same side as the kid she didn't like so they weren't defending each other. DD was a lot happier.
