The midfielder’s ankle rolled under him after he battled with Antoine Semenyo and he collapsed to the pitch in agony.
He let out a piercing scream as the severity of his injury soon became apparent.
His team-mates were left gobsmacked by the injury and put their hands on their heads in dismay.
Play was immediately stopped and the referee hastily waved Forest’s medical team on to the pitch.
They moved quickly to treat the fallen Danilo, with stewards covering him with a makeshift tent.
After eight minutes of treatment, Danilo’s damaged leg was braced and he was stretchered off the pitch.
Both sets of fans at the City Ground applauded the 23-year-old as he was taken off and sent to the hospital.
Another said: “Pray for Danilo, jeez. It’s not looking good.”
And another said: “Oh my god that is utterly horrific for Danilo.
“Wishing him a speedy recovery.”
One remarked: “Our thoughts are with Nottingham Forest’s Danilo who appears to have suffered a season-ending injury during their first game.”
Another chimed in: “Get well soon, Danilo.”
Danilo’s visibly rattled team-mates tried to refocus after his horror departure.