Let me start by saying I am a huge Witten fan. I think he has been a great player and a great person to have on the team. That said, and I know I will ruffle some feathers with this, I don't fully agree with the article's premise of Witten being an "undisputed leader in the Cowboys locker room". I think he's definitely a leader, but "undisputed" implies that everyone listens and follows him and I do not believe that to be the case.
I think Jason leads by example and I think he is very vocal with most of the players on the team when he's on the field. However, I think he tends to shy away from players who are more animated or vocal, especially off the field. A good example of what I'm talking about was last week when he was giving an interview in front of his locker and Dez was going off on the media. He paused his interview and looked around the reporters to see what was going on. After a little time, he went back to his interview like nothing happened. An "undisputed leader" would have excused himself from the interview and walked over to try to calm Dez down. A leader takes control of situations like that before they get worse. Once they get really bad, no leader can calm the situation, so good leaders are proactive.
The bottom line is that one could argue he's an undisputed leader on the field, but I don't think he's an undisputed leader in the locker room.
Just my thoughts of course ..