I am level 5 too, so i might be able to help.

What is his worth? look at other 20 yo in the Transfer list and compare the worth to the best and verify if he is a fast trainer. If he is, then he is worth keeping. I have a 20yo I was lucky to get for 5 tokens(and I mean lucky, 39Q and 2 pts from 40Q!):



If your 20yo is worth as much as this or more, then keep him and train the bugger. He will be around for a few years. Just put it down to him having a bad year.

If he is worth less than this, it is debatable to keep him. Buy someone to replace him, then sell him. Or put him in reserves and see if someone will buy him for a few tokens, which is better than nothing and just money on the transfer list.