The back is extensively gray already, and the flanks have a lot of gray coming in. The Wigeon hybrid situation is a tough id challenge. Everything looks good for a bird transitioning to alternate plumage as far as the body plumage goes.

The tiny green area around the eye was never visible to me in the field, though we were obviously fairly distant. But, I had stellar looks at the bird through my Kowa 883, and even at 60x never saw the green. This little spot of green in this area is commonly seen in photos of Eurasian Wigeons in the Old World, so I don't think it is an indicator of hybrid origin, like a green stripe ala American Wigeon is.