Assombalonga has been ruled out for 12 months with a knee problem which he picked up during the Reds' 3-0 win against Wigan Athletic in midweek.
The striker had to be stretchered off in the latter stages of the match, and the severity of the injury has turned out to be even worse than even the most pessimistic Forest fan would have feared.
Assombalonga's absence will leave a huge void in Forest's first team, and Freedman was in no mood to play down the impact of his injury on the team.
“It is disappointing and it is mainly disappointing for the lad. I am disappointed for him, but things like that happen in games. We just have to make sure we give him support,” he is quoted as saying by The Nottingham Post.
“I am not too sure what the exact damage is, in terms of the injury, we have just been told that it is an injury that will keep him out for 12 months.
“It is a blow for the player more than anything, because he is a huge player for us, he has scored 15 goals for us already this season. I am disappointed for him more than anything."
Naturally, the hope is that an injury this severe will not hamper Assombalonga's development as a player too much.
The striker had looked ready to make the step-up to the top level, but his spell on the sidelines is a major set-back for someone who is at a critical stage of his career.
Forest also have the problem of trying to find a replacement for Assombalonga as they are under a transfer embargo.
The Reds are unable to pay a fee to sign a new front-man and, therefore, finding a player of similar of ability on a free transfer is going to be virtually impossible.