It is a red card in my opinion:
- tackle comes from behind, player cannot see it coming and is thus extremely injury prone
- the player was already gone, the tackle was more than desperate
- he tackles with both feet and thus is whole body weight, multiplied by his speed
I think you guys in the UK have a different view on this, because you all really like physical football, but if this tackle was no red and allowed, there would definitely a lot of ugly injuries in one season. If in doubt, you need to protect the player anyway.
Up to the 90s, this would have been a straight red in every single case. But after 2k I feel that the referees have got some additional baggage from their managers, like "don't give a red" and disrupt the game.