Great use of bokeh. Per the challenge goal, it really enhances the subject by giving a context for the scene without providing detail which steals the attention away from the ref.
Composition is good, lighting is good. This really has the feel of a late afternoon game.
Pants on the ref are a bit overexposed, but I think all the important details in the rest of his outfit make up for it.
If possible you should try and submit at the full dimensions allowed by the challenge rules.
I would have preferred to see a facial expression - one typical of a ref making a call. Or even if he were blowing his whistle, then photographing the back side of the ref would be acceptable. For me this is simply a stripped shirt in front of a blurred background.