Indoor sports are demanding because you need both fast shutter speeds and enough light for autofocus. A 70-200mm f/2.8 helps, but it won’t solve everything on its own.

Start by shooting the lens wide open, or close to it, at f/2.8 to gather as much light as possible. Use a fast shutter speed to freeze action—typically around 1/500s to 1/1000s for many sports. To support that shutter speed indoors, expect to raise ISO substantially.

If your images are still blurry, it’s often motion blur from too slow a shutter speed rather than a lens problem. If autofocus hunts, that’s common in low light because AF needs contrast and edges to lock on. Try focusing on areas with clear contrast, such as uniform details, faces, or strong edges, rather than flat or low-contrast surfaces.

A remote flash can help if the venue and rules allow it, since adding light improves both shutter speed options and autofocus performance.

In short: use f/2.8, keep shutter speed high, raise ISO as needed, and aim AF at contrasty subjects. Indoor sports usually require balancing all three exposure settings carefully.