The Baggies currently sit eighth in the Premier League after an excellent campaign under their Scottish head coach, who succeeded Roy Hodgson last summer, with the trio all playing key roles in their rise up the table.
And now West Brom's 49-year-old boss is desperate to keep together the current squad and feels there are certain players the club simply must retain if they are to progress further.
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"I think, come the summer, the ones that we have to keep - I want to keep - will still be at the club. There are one or two behind them in the queue, but we can't speak to everyone at the same time."
Meanwhile, Clarke addressed the three-match ban received by Mulumbu after he lashed out at West Ham's Gary O'Neill, kicking the ball at the Hammers midfielder during their clash on Saturday.
"It is an internal disciplinary matter," he continued.
"Youssouf was very apologetic. I think you could tell it just came from sheer frustration at the disappointing performance.
"It is out of character. I have never seen anything like that from Youssouf in the time I have been at the club. He let himself down but he knows that and apologised."