The first sports photographer I looked at before starting my photography was Bob Martin who from looking at some of his photos specialises in a shallow depth of field for most of his photos examples above. These photos were all taken from http://www.bobmartin.com/gallery/test-gallery/.
These photos are all a very effective use of a shallow depth of field as they make you focus on what's important in the photos instead of looking into the background at something irrelevant.
The second sports photographer I looked at was Adrian Dennis, looking through his work I realise that some of this slow shutter speed shots were really interesting. With slow shutter speeds, you get the effect of how fast the person I going. These photos above are from http://adriandennis.com/sport/