Tributes were paid to former Millwall defender, Motherwell and Crewe Alexandra who was found dead at his home.
Police were called on Tuesday afternoon at Cottam near Preston, with the death not believed to be suspicious.
A Lancashire police spokesman said, “We were called at around 1:30 p.m. today (May 26) at an address on Greenfinch Avenue, Cottam, to reports of a sudden death.
“We attended it and unfortunately found the body of a man in his twenties.
“There do not appear to be any suspicious circumstances surrounding his death and a file will be sent to the coroner in due course.
“Our thoughts are very much with his family and friends at this sad time. “
After climbing the ranks in Brentwood Town, Mbulu had spells in Millwall and Motherwell, and joined Morecambe after his release from Crewe Alexandra in January.
He played three times for Morecambe in League Two this season, making his debut for The Shrimps in a 2-0 win at Walsall.
Mbulu joined Millwall on the Brentwood Isthmian League side in 2015, but has not made an appearance for Lions in the league.
Morecambe said in a statement, “He was only 23 years old and the news of his sudden and untimely death came as a shock to all of us.
“Christian came to the club in January and has proven to be an extremely popular member of the team.
“His loss will be painfully felt by all who have had the pleasure of knowing him. “
Millwall Academy director Scott Fitzgerald said, “This is truly shocking and tragic news and our hearts go out to Christian’s family and friends.”
“Christian was incredibly popular with teammates and staff during his stay here and seemed ready for a very bright and successful future in the game. He was very professional, hardworking and courteous and stayed in close contact with many people within the club.
“We all have so many great memories of Christian from his time with Millwall and it was so encouraging to follow his progress and development as a player from afar. We are really shocked and saddened by this horrible news. “
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Motherwell President Jim McMahon added, “We are shocked to hear the news of Christian’s death.
“He was such a nice and nice young man that we liked to have around Fir Park.
“Our thoughts are with his family during this incredibly difficult time. We hope that their privacy will be respected by all as they try to cope with their loss. “