The stance looks like a rooster giving you the stink eye, about to ruffle his neck feathers. It's comb also stands straight up, so I'd think it is a roo. Roos are more colorful and have longer tail feathers than hens.
PS - I don't know much about sex links, but I just did some reading, and the male red sex-link is supposed to be mostly white (like yours). So I'm not sure how it slipped into a batch of pullets.