Play time turned into an opportunity to practice a few more commands.  Perhaps commands is too strong a word.  Associations is better.  I had just stumbled across the Dog Training Homework section on Peggy's site, and saw that we could work on "Stay" and "Drop" and "OK".  I think this one will take some repetition.  "Stay" was more coincidence than response.  "Drop" was just me tagging the event, and "OK" was essentially validation of Gunnar's decision to chase the ball.  Baby steps.