Mulumbu joined Celtic in the summer of 2018 on a free transfer after he left Scottish Premiership rivals Kilmarnock at the end of the 2018-19 campaign.
Much was expected of the former West Bromwich Albion midfielder when he moved to the Hoops, but the 32-year-old struggled to make an impact at Celtic Park.
According to WhoScored, the DR Congo international was able to play just once in the Scottish Premiership and managed just 85 minutes in the Europa League for Celtic this season before he moved to Kilmarnock on loan in January.
Mulumbu has suggested that it was due to the presence of Christie that he failed to establish himself in manager Brendan Rodgers’s team.
“It was hard at Celtic,” Mulumbu told The Scottish Sun. “You are going into a team which is winning every game and you see players like Ryan Chistie, who deserved to play, get his chance.
“I was frustrated, but I was also happy for Ryan because he and I were in the same situation. You could say he took my spot, but he really deserved it and I just tried to stay fit.”
Christie returned to Celtic in the summer of 2018 from his loan spell at Scottish Premiership rivals Aberdeen and has been superb for the Glasgow giants so far this season.
According to WhoScored, the 23-year-old Scotland international midfielder has made 14 starts and five substitute appearances in the Scottish Premiership for Celtic so far this season, scoring eight goals in the process.