From my experience, typically when you see comments like his, it's because the coach is frustrated with the leadership and effort on the team. Those things are hard to coach. Sometimes losing just one player can completely change the dynamic of a team's chemistry and leadership.
We fans get caught up in what I call the Playstation mentality of sports, where we assign players a status and base our expectations for the team off the sum of those statuses. Problem is, Playstation doesn't factor in chemistry or leadership. It's probably just coachspeak from Mullen to try to motivate his troops, but my guess is he's dealing with a lack of leadership within the team and/or a group of leaders that either didn't understand or forgot how hard the team had to work to get where you did last year.
I know Nutt gets criticized for talking about managing expectations. I believe that's something he struggles with though as a coach. He's a players coach, and I think at times he has a hard time keeping a team hungry when they're being praised too much. That's what Mullen's comments sound like to me. He sounds like a coach that's fighting with a team that thinks it has already arrived, when in reality you've never arrived. If you saw the Mike Leach Youtube of him cussing in the locker room. He was dealing with the same thing at TTU in that clip. Sometimes all it takes is a coach berating the team to re-instate the hunger. Sometimes it takes a wake up call game, like an unexpected loss or a poor performance in a win. Sometimes a team just never comes together. Either way, that's what Mullen sounds like he's fighting from his comments.