The midfielder could be away for a number of weeks at the turn of the year because of the DR Congo's Africa Cup of Nations campaign in South Africa.
Despite admitting that Mulumbu is a key player, Clarke feels that he has the reinforcements available to cover any temporary departures.
"We spoke about it at the start of the season. We knew we had the possibility to lose Youssouf," said Clarke. "We discussed it and we think we have enough in the squad to cover any absences in January.
"If not, it's a good month for it because the transfer window is open again in January, and if you need to address the situation you can.
"Many things can change between now and January but as things stand we're comfortable with the squad we've got."
Mulumbu joined the Baggies in 2009 from Paris Saint-Germain.