Mulumbu has formed a fearsome midfield partnership with hard-tackling Yacob since the Argentinian's arrival at The Hawthorns on a free transfer from Racing Club in July 2012.
Steve Clarke has tinkered with his central midfield combinations so far this season - but Yacob is ever-present Mulumbu's preferred partner in the holding role as he gives him the 'freedom to go forward'.
The duo were reunited for the 2-1 win over Manchester United at Old Trafford and also performed well during last weekend's 2-2 draw at Chelsea.
And DR Congo international Mulumbu admits their understanding is almost telepathic due to 'hard work' on the training pitch.
"He protects our defence really well and that gives me a little more freedom to play and go forward," Mulumbu told the Birmingham Mail. "In training we work really hard together.
"It helps that I speak a little Spanish and that's how we communicate - but Yacob is one player you do not need to speak to - he knows the role he can fill.
"Every time I play I know where he's going to be - I know his position.
"It is easy for us to communicate because we feel the same way.
"The best thing with Yacob is that he never stops running. He offers me protection. For me it is unbelievable how many balls he manages to win.
"When teams win quite often it is the striker who receives the praise.
"But when you see how far he runs, you'd be surprised - it's unbelievable."
Mulumbu believes he has improved as a player during his time at The Hawthorns, and will celebrate his fifth year at the club in two months' time.
The 26-year-old has made more than 150 league appearances for the Baggies, and said: "I have improved a lot over my time in the Premier League.
"When you play with good players you are going to improve because you need to step up.
"And the fact is I have managed to escape injury so I've played a lot of games in the Premier League.
"That means I've played in the best league in the world against the best players.
"Every game at this level has a big intensity and that has helped me improve my game - that's the Premier League."