Assombalonga signed for Forest from Peterborough in 2014, and he made a blistering start to life at the City Ground.
The powerful front man netted 15 times in his first 32 appearances for the Reds, but his progress was cruelly halted by injury.
Assombalonga damaged his knee ligaments in February, and MacAnthony believes that the injury stopped a mega-money move at the end of the season.
“Assombalonga would have gone,” MacAnthony said.
“He was on for 20 goals [last season]. He would have gone for probably £12-£14 million in the summer [had he stayed fit].”
Assombalonga has still not returned from that injury problem, with his comeback to action taking a long time.
The 23-year-old has been severely missed by Forest during his time on the sidelines, as he was their main goalscorer before picking up the knee problem.
Assombalonga is finally closing in on a return to health now though, and he could make his comeback in the next few months.
Forest will be hoping that the striker can pick up where he left off, as they look to mount of play off push in the second half of the campaign.