With Everton holding an option to sign him permanently at the end of the season, Moyes believes he could just have another Goodison sensation on his hands.
"We did it with Steven Pienaar when he was out in the cold [at Borussia Dortmund], and it happened with Mikel Arteta too, who couldn't get a game with Real Sociedad when we took a risk on him," Moyes explained.
"Royston has a big talent - you don't get Real Madrid signing you if you don't have that. But let's put this in the right box. It didn't work out for him there and we signed him at the last minute.
"It could work out for us, but sometimes it doesn't. It's a little bit of the unknown right now, but we are hoping he will work for us and we can sign another talented player."