When you are playing Fetch with your dog - don't be upset if he runs to get the toy then plays with it before coming back to you. Unless you are working on competitive skills, it really doesn't matter if he comes back right away or not. The purpose is to have fun with you! If part of that fun includes playing with the toy for a few minutes - what harm does it do? 

My Beardie regularly chases his toy and lies down with it to have a chew. He either comes back when I call him or he comes back when he is ready for the next toss. Either way - he knows the combination of me and a toy equals fun!