It looks like "The Walking Dead" Season 7 will be following the story in the comics where Negan makes one of Rick's gang as his loyal dog. The only difference is that he could be training Daryl instead of Carl as seen in the comics. Daryl's character was never really a part of the comic but the showrunners really like Norman Reedus' audition that they created a role for him.
Now, Daryl is one of the lead stars of the show and is undeniably one of the fan-favorite characters. Unfortunately, his character may also complicate how the story should go which should be, at least in some way, be based on its comic story. This led people to speculate that showrunners have decided to make him be the character that Negan takes and trains to be his loyal dog instead of Carl.
The latest episode of the series coincides with the story in the comic book where Carl runs away with Negan's truck after he got disappointed with his father's submission to Negan. As Negan returns to his base, Carl open fires at his men using a machine gun and successfully killing a number of them. Surprisingly, this impresses Negan and convinces him that he wants this boy on his side.
The person that Negan will train as his loyal dog will not really go through rigorous training as the comics' only shows Carl being adopted by Negan. The worst thing Carl has to do for Negan is to walk without his eye bandaged. Carl is never fully converted in the process of the training but it confirms the fact that Negan will have someone from Rick's team to be his dog.
The story in the comic gives the audience a preview of what Negan plans to do with Daryl. Many believe that the training can happen soon as Negan already has Daryl in his possession. Besides, Carl in the comics was about nine years old which explains his hot-headedness that urged him to do a suicide mission while the Carl in the series is a 17-year-old mature boy.