But the Congolese midfielder is nowhere to be seen in the build up to their game in Germany later.
And as far as we can see there has been no explanation as to why he wasn’t involved in the weekend win over Hibs or seems set to miss out tonight.
Brown limped out of the Hoops’ 4-2 win over Hibs on Saturday after just 21 minutes and hasn’t travelled for tonight’s game.
Tom Rogic’s injury leaves another gap in midfield so you’d expect Mulumbu to definitely come into the reckoning for a starting spot.
He was impressive despite Celtic losing 3-1 to Red Bull Salzburg three weeks ago.
So we really can’t understand why Mulumbu appears set to miss out.
Perhaps it could be down to his public comments earlier this month about Celtic not being worried about their Scottish Premiership rivals – despite Hearts occupying top spot in the league and the constant threat from Rangers, Hibs, Aberdeen and Kilmarnock.
Mulumbu made those comments on October 5th and was on the bench for the 6-0 beating of St Johnstone just days later.
But his absence since has been curious, with no official word of an injury coming from the club.