There seems to be a lot of white RBs and WRs that are of Irish ancestry. I wonder if the Irish have a slightly higher propensity for those positions than your average white. The Irish are a less numerous ethnic group than most Europeans and I can name plenty of top speedy football players that are Irish. The Irish don't do quite as well in strength competitions, boxing or wrestling as Slavic or Nordic peoples, but seem to have great agility and short area burst. Go Irish!