He should have a key worker.
That's not to say that the others don't have anything to do with him, but it is one person who is specifically assigned to keep a very close eye on him, and have an overview of his progress.
For my dd, the key worker is also the person that if I have any concerns, I can go to.
By concerns, I mean things like, when dd was having trouble potty training, I spent ages discussing it with the key worker, making sure that we were all going to be doing the same things to avoid any confusion for dd.
Her key worker also fills out a sheet every half term, giving a summary of the half term (themes, progress dd has made with her language, and comments on anything I've asked them to support her in, like sharing which is not a strength in our house!). I then return it to them, with additional comments (if there's anything I want them to do particularly, like 'please continue to help her understand the concepts of sharing and turn taking!'). It is the job of the key worker to ensure my requests are being met, by making the other nursery staff aware as well as involving herself directly with dd.
At dd's nursery, I didn't know who hers was for a while, but that was deliberate. They told me they didn't assign them straight away, but waited to see who the children gravitated towards and then tried to organise it so that person was their key worker. That way, if she's upset, there is someone who has primary responsibility for looking after her, and it's someone she has 'chosen'. That person also has primary responsibility for communication with me.
However, she is by no means the only one to come out and say hi and collect dd, or drop her off to me when I collect her (I may see her three days out of five). The others are just as friendly and dd seems just as happy to trot off with them, and I am free to discuss any issues or queries with any of them.
If you haven't got a key worker, then who is keeping track of what he's doing? I don't mean which toys (if any) he's choosing, but who is tracking his ability to interact with other kids, who would you talk to if you were potty training and needed them to do the same things as you etc etc? Long-term style tracking?
It's worth knowing that dd's nursery has not had a single 'outstanding' for anything. It's scored 'good' and 'satisfactory', and is not wildly popular. But it is absolutely brilliant - the care has been second to none and their support in dealing with some quite difficult issues has been superb - and I recommend it to everyone I know. Demand for places is low presumably because it's not outstanding, but I don't care. They care for the children, even if it doesn't tick boxes! (They even organise weekend walks sometimes,so all the parents can meet each other and the kids can all have fun together!)