Nelfoos - if Valencia was attempting to make a tackle then yes it probably is a yellow card. He doesn't make a tackle, he clearly and deliberately kicks through the opposition player's legs.
You can watch it here: https://streamable.com/goxnn
The close up shot from behind says it all. It's not a tackle. He's kicked him. The only criticism you can point at the ref is that he lost control of a friendly when he didn't punish their poor tackles.