This is how i see it. To give the lad a couple of months to get himself back up to speed after a 4 year break out of the game, and then a stop / start year at Chessie not helped by them having a poor physio team, is only fair. In my mind, I never expected a totally fit and ready Ched Evans playing up front for Utd in August. If he's still not fit and ready to go in October though, then and only then will i start to have a couple of doubts. Give the lad a chance, he could be a snip for us.
The big thing, as i understand the physiology aspect (others may know better) is that its not the playing which is the problem, but the recovery.... Which in turn makes the playing a problem too. Fitness wise (cardiovascular) he will be able to last 90 mins. In terms of physique, he's clearly worked hard over the summer
Muscles and joints won't be accustomed to playing and recovering regularly, so he will pick up niggles like he did at Chesterfield last season. Perhaps the season he had there has been detrimental as well (not to criticise Chesterfield). The club and player will have wanted to be back playing and if he felt good then why not?
The Sports science aspect, again i'm far from being an expert, is driving this. Wilder has pointed to this as well during pre season (Stocksbridge game as an example). Whilst Ched will declare himself fit and be prepared to play through a niggle, there will be a programme for him which takes the impact of football (running, jumping, twisting and turning) into consideration. It will also monitor his fatigue based on performance data, which is linked to recovery times.
These programmes are quite dynamic and whilst being cautious, there will be opportunities to accelerate his involvement. As I said on another thread, the 'hip' issue might be precaution and if it was something hanging over him from last season, it will be handled with more care.
Final point, summer games are tougher as the pitches are harder. Malaga will have been a hard pitch, even with watering, it will have been drying out during the game, same with Chesterfield. The benefit of our pitch is that we have a very new sprinkler system, but it will still be quite hard.