Holt admits Benteke's injury - picked up in training - could not have come at a worse time.
He said in the Birmingham Mail: "That's the most frustrating thing. He'd just got that smile back on his face, he was playing well and scoring goals.
"He was laughing, joking and enjoying himself and that's where football is a cruel game. The good thing for him is he's young enough, he can go to World Cups for the next eight years - and the Euros.
"With the mentality he's got, the quicker we can get him back on his feet the better."