Have to agree with TBB, Molsey
A good pre-season is important for all players, but for some it is far more critical. Some players take a while to get back into the swing after early injuries. Kouta last year took a long time to work his way back into form, although when he did he was excellent. I remember his early attempts at kicking for goal were deplorable, and that had to be a lack of confidence. Fevola finds it hard to regain form when he has a few weeks off. Others like Jonathan Brown are able to hit the ground running, but they are in a minority.
But at least those big-name players have the benefit of knowing that they are proven AFL performers. It is harder for players who have not yet consolidated a place in the team. For Callum Chambers, Livo, and ADL, there would have to be nagging doubts about whether they are up to it, and this will make it more difficult for them to regain touch and confidence. Unfortunately, when the team loses confidence and self-belief as well, this is all the more difficult. For players who have not had much of a preseason, the likelihood is that they will make some bad decisions and skill errors early, which will start undermining their confidence. Moreso in ADL's case as he was thrown between ruck duties (when he really is primarily a forward), defence (and he doesn't have the innate defensive skills or powerful body to play in a key defensive post) and attack.
Sure, it would be preferable if ADL had cast-iron mental toughness like JB. But this could be said of a lot of other like Kouta who have not been able to immediately regain touch by sheer willpower.
There would have been a loss of fitness, both general and match fitness, as the result of the injury. The adage is that a player is at his fittest when the season starts, and then he tries to maintain that level as much as he can. ADL must have started with a lower level of fitness than he would have liked. And this won't necessarily be reflected in being benched or unable to run. He may have had enough aerobic fitness from running laps and the like to keep moving around the ground in a jog (although maybe if Pagan had more tall options he would have reduced his playing time accordingly). Despite being able to move around in a jog, it is likely that his lower anaerobic fitness level (given the drills he missed are built around intermittent bursts of activity) would have reduced his ability over the course of a game to explode into a sprint. This would have happened more quickly given the ruck role. And fatigue would lead to an increase in skill errors like dropped marks, poor decision-making and poor kicking (exacerbating the predisposition towards those errors created by a loss of confidence).
The other aspect is that players who have not enjoyed a full pre-season through injury tend to be more susceptible to injuries. And often these further injuries are caused by the player consciously or subconsciously protecting his original injury. So the good knee ends up causing trouble (which is one reason why trainers tape up the good knee to correct this tendency). Or in this case the good foot ends up being stressed. Perhaps ADL was restricted by the original injury, whether this was for medical or psychological reasons.
But all of this is just an attempt to describe the differing effects of a loss of a preseason. But do we need to be that technical? Surely those of us who have played sports know that a good preseason helps and without one we are always playing catch up. And surely those of us who have followed the AFL for a long time have seen players struggle to overcome an interrupted preseason time and time again.