HMM. $50.00 That is really, really cheap for a fast sports lens. I will be the first to admit I am no expert on the older lenses. BUt I believe you may be able to have somone else give you some info. Couple of questions to think about. How well are the places you are shooting? Realistcaly if they are not super bright gyms or you are using a flash a good sport lens will cost you upwards of $500-$1000+ . But if you can get close that 50mm at about $200 will be okay. It will not get you tight shots but you could do some creative cropping to help. Good luck in your search. I have the Sigma 70-200 2.8 and it works well for me in good lighting. Cost me $600 about an year and a half ago. That was then, they are selling around $800-$1000 now. Again good luck and I am sure others can offer older lens suggestion that will work.