To me this chappie would be an immediate release once he is recovered. One of the greatest predictors of an injury re-occurrence is prior injury. Let's look at his injury record:
https://www.transfermarkt.co.uk/isaa.../195481/plus/1
In the last four seasons he has had three major injuries. The ACL I can well understand he was omitted for 438 days and 64 games. That was a serious ACL injury, however optimistic anyone wishes to be. Following that he had a hamstring injury, which kept him out for just 5 days. That seems awfully short for a hamstring injury, and I would question who made that physio assessment to allow him to return after just 5 days. As a result, it re-occurred and he has been out for 488 days and 69 games. That is the problem with rushing players back.
According to top class physios, five factors affect a player's recovery from injury:
1. Degree of injury. Grade 1, 2 or 3?
2. The age of the player. Your body doesn't recover so well after late Twenties. If you are in your teens or early Twenties your body recovers a lot quicker. In most cases, fully with today's modern techniques and clinical precision.
3. Prior history of the same injury
4. How quick it was dealt with. For example, was it diagnosed, cared for (protected) and treated quick enough?
5. Quality of physical rehabilitation. Is the gym up to scratch? Is your physio an old fart or au fait with the latest and best rehabilitation techniques?
6. Mentality of the player. Mental commitment to an extensive rehab programme needs a person with a strong mind. The weak -minded player will skip his rehab or not be disciplined in their daily rehabilitation routine. Kinesiophobia is also often underrated in player recovery. All the above 5 factors may be on your side, but if you lose confidence in your knee, did not commit to your rehab, do not believe in yourself or your body enough to trust the moves of your body. If you have had ligament or cartilage injuries you must trust yourself to twist and turn as you did if you have recovered. If you have had muscular injuries but have recovered you must go full pelt on a sprint and not hold back. Kinesiophobia is a fear of your own body following a major injury, and can kill this confidence. The player may no longer trust his body, which means that even if the above 5 factors were in your favour you will not recover well enough and it affects elite performance.
That said, what one must now do as a coach is now form a view. Keep or get rid. You are paying him a salary. He has lost 931 days of football, and 134 potential games. That is three full seasons of no return on his wages, and no football contribution. A one-off ACL is recoverable a double hamstring injury and the length of being out suggest it is a tall order for what as an average player to return to his average form. Being out for a year with a hamstring tear either suggest a Grade 3 or he is suffering from Kinesiophobia.
At 28, out of the game for three years, I would say all the 6 factors above are not stacked in favour of a performant return. With regret, for me it is a very simple sell / release decision for Isaac Vassell.