This is an interesting incident. I have seen players dismissed for this Mings vs Zlatan a good recent example, but if you look at the clip after the initial challenge Mings is off balance as he has made contact with the Reading defender and is trying to stay on his feet and during that his leg plants on the Reading players face. Foul yes. Yellow card I can see that decision, red card you can certainly call it as SFP because of the injuries no caution can see that as well he is off balance trying to keep on his feet and lands on the defender he isn't looking down but straight ahead so it could be classed as accidental and one of those things. I watched it on the small screen first then enlarged it and I can't see a stamp as such but a continuation of his running. Like I say all three results I can see reasons for. Also the ref has one bite at the cherry for this and the replay is in slow motion so not a real indication of what it looked like in real time.