I'll be honest, I don't know.
If I am to make a barely informed guess?
Word is that what Benford's injury is a torn meniscus. Some people are able to play on it, some aren't it depends on the swelling. Recovery is a few weeks if you need a laparoscopic surgery, but you need swelling to go down to be able to do it.
In comparison, if Bernard's sprain is a common lateral sprain there isn't a surgical option, just rest (elevate and ice) and pain management. That he's on the field practicing and stretching is a decent sign that it might have been a lower grade.