I was going to stay out of this conversation regarding Bird, but **** it, I have trained people for 20 years so I think I can offer a few insights. First and foremost is some people just do not have great genetics when it comes to body composition regardless of how they train. Some people can look at a weight and gain muscle while some will never have a visually appealing physique. That said...
When you are an athlete that makes a living with your body and don't have the worlds best genetics, you had better be able to have a diet that does the body favours. I have seen a few photos/videos of Jack Bird at chow time and it wasn't pretty. The bottom line is what separates the good from the great from the OK is the commitment in training and diet. This is even more so when a person has ectomorph qualities as Bird does. The other thing is needless to say he should be busting his ass in the gym IF and I say if because I don't know the extent of his injuries. More muscle mass = leaner. Why? Because when you have more muscle you will always be leaner because you burn more calories 24/7. Think of the body as an engine. A V8 burns a lot more fuel than a 4 cylinder motor. Roberts and Oates are V8s while Bird is a 4 cylinder.
Often you will see that diet is a reflection of training and vice versa. Again, it all comes down to discipline and a persons ability for discomfort and being able to overcome discomfort (not having quick lousy food when you want it, or training hard when you don't want to train hard) vs being disciplined and reaching the end goal.
At this point I would guess that Bird needs to work harder on his discipline in both areas. My guess is he has very good natural ability as a footballer but is far from being his best and hence why people find him a let down. Still...I don't know what the extent of his injuries are but can tell you for certain that he needs to be way more disciplined than he is. There is no reason that a soon to be 50 year old like myself should look a lot better than him.
I would not let him in a Broncos jersey again till he gets fitter and proves himself in the lower grades.