The 25-year-old defender, who is a free agent, left Barclays Premier League outfit Crystal Palace at the end of January and has been training with Blues this week.
"Darcy is with us," said Clark. "He is one of those players that falls under our remit because he’s out of contract now after he had his contract with Crystal Palace terminated by mutual consent.
"I’ve always been an admirer of him from his Cardiff City days. I spoke at length to the Wales national team manager Chris Coleman, who speaks very highly of him. What impressed me about the lad is that he wanted to come in and show us what he was capable of in terms of training with us and possibly playing in a couple of development games.
"When a player of his stature is prepared to do that you’ve got to open the door for them."
Whilst Clark says he has been impressed by what he has seen of the former Palace and Cardiff City defender, he says any talk of an immediate deal is premature.
"I’ve got to say in the first couple of days of training he’s impressed me and my staff immensely," added Clark.
"We’ll see what transpires, but there’s still a long way to go in terms of him playing a couple of games and also if funds are available."