Alternatively, he was chasing back to win a ball because his teams last away win was 10 months ago.You're rarely ever going to be able to judge intent on the pitch, so to me that's a fool's exercise. But if you want to play the intent game, do you believe that Son intended to foul Andre Gomes? I don't believe for a second that he intended to ever injure him that way (and I would feel that way about 99.9% of footballers), but he absolutely was trying to foul him for the elbow just minutes before.
To decide with that he "absolutely was trying to foul him for the elbow"is a dangerous assumption to make...following that logic there is an argument to give him a stretch for assault. After all, it is effectively saying he deliberately have him a premeditated kick.