Mulumbu has started every league match for Steve Clarke's side this season, continuing his impressive partnership in central midfield with Yacob.
The duo have become well acquainted following Yacob's arrival from Argentinian side Racing Club in July 2012, and Mulumbu is appreciative of his colleague's efforts.
"It helps that I speak a little bit of Spanish and that’s how we communicate," he told the club's official website. "But Yacob is one player you do not need to speak to. He knows the role he can fill.
"He protects our defence really well and that gives me a little more freedom to play and go forward. Every time I play I know where he's going to be.
"The best thing with Yacob is that he never stops running. He offers me protection.
"For me it is unbelievable and how many balls he manages to win.
"When you see how far he runs, you’d be surprised - it's unbelievable."
Mulumbu is satisfied with his personal progression since joining West Brom in 2009, but determined to continue developing as a player.
"Every game in the Premier League has a big intensity and that has helped me improve my game – that’s the Premier League," he added.
"I can improve again. I just need to keep training hard."
