He just stops and try to reach them with a leg, but they would've already past. He should be ready for their sprint. He doesn't do that, unfortunately; which is one the basics of defence.
I see him do that ALL the time, in situations where he should just run alongside an attacker instead of going for that do-or-die tackle. It is quite worrying to see him do that all the time I have to say. It makes me feel like he has trouble judging the easiest of situations at times.
If he was standing in a half turned position, as he should be, he would have the option to run with the player, rather than having to make a do-or-die tackle every time.