j elky,
That Tamron 28-75 f2.8 lens is a great lens. I used it for many years prior to the 24-70mm f2.8 coming out. I have lots of friends that still use it. It is made with the XR glass so clarity and sharpness are not an issue. It is prior to the Vibration Compensation being added but you should be fine for sports with it. Also it is a lens designed for Full Frame but can be used on APS-C cameras. The advantage is you are shooting more of the "sweet spot" with a cropped sensor camera like yours.
