This SP article on "what to eat after your workout" is really going to help answer your question: www.sparkpeople.com/resource/nutrition_art
You need carbs and some protein. Usually a protein shake is not the answer.
Also...what is your typical protein intake most days of the week? Are you eating within your SP protein range? IF so, you are meeting need. Extra protein from that shake is not necessary and only a source of calories.
Hope this helps
SP Registered Dietitian Nutritionist