The slide is supposed to protect Quarterbacks from hits like this.
Teddy Bridgewater knocked momentarily unconscious by a late hit on a slide by Lamarcus Joyner pic.twitter.com/D4Sn9TBsLK
— The Cauldron (@TheCauldron) November 8, 2015
Sometimes it is a bang bang play, but in this case it appears that Joyner had plenty of time to pull back but chose not to.
Joyner was not penalized on the play.