Speaking to Sky Blue Player, Boothroyd said: "There will be a couple more ins and outs because I think you need a tight squad with players you know you will use.
"Marlon King has been training with us for the last few days and we have put him through a raft of tests to measure his levels of fitness.
"Contract talks are still ongoing but I would like to bring him here and now it is just a case of coming to some sort of agreement and I'm hopeful we can do that."