Rayo are set to face Unionistas, with James' inclusion the big headline.
Perez said: "James didn't play in the first qualifying round due to a small annoyance, as I explained. He is now in good condition and will be with us tomorrow.
"He will play tomorrow.
"I don't like to talk about individuals in a press conference. The coach, when he makes decisions about who plays and who enters the field, always guides himself on how he prepares the team against an opponent. In this case, I reiterate the same concept: I am very satisfied with him, he trains very well.
"I have a large squad, with many players. I try to manage it in the best way possible. I am aware of James' level. He must continue as he is doing day after day. I will not go into tactical details."
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