Yes you would. I saw it last night. Cynical bit of gamesmanship to ruff up the class where the non-kicking foot lands. The player did slip in taking the penalty.Red is not possible. YC for the 'unauthorised marks', but you probably wouldn't think anything of that if you had seen it....
Apart from the Yellow card, what else should the referee do?
Most 'keepers aren't on their line when the kick is taken so catch him up for that, because it's much more valid.You mean, if he sees it and doesn't like it? How about this: he can order a retake for encroachment. And if they don't score the second time, he can order another retake for encroachment.