Hille, 27, was in space on the wing and jumped for a high pass in the second minute of the match, but his left knee buckled under him as he landed forcing him immediately from the ground with the aid of two trainers.
After an initial examination on the bench, Hille was taken to the change rooms for further assessment by the club's surgeon with the early prognosis a grim one.
"It seems that it will be the worst, but that has to be confirmed," coach Matthew Knights said after the game.
"We're thinking it's not going to be good, but we're waiting on confirmation of that."
Hille's loss was a dark point of an otherwise proud day in the club's history as his teammates went on to upset the Magpies in thrilling fashion in the dying seconds of the game.
Knights admitted it had been difficult news to hear, but he had little time to dwell on it.
"I had to move on quickly, but I was really devastated, because David is an outstanding person," he said.
"Being in the prime of his career he is a huge player for us, so it was always going to be a big time blow. Thankfully our players adjusted beautifully.
"Patrick [Ryder] went into the ruck and was able to play virtually the rest of the game in the ruck."
Ryder, a pinch-hitting option in the ruck to this point in his career, earned the Anzac Medal for his magnificent display in Hille's absence. Knights forecast a full-time move into the centre square for him, but agreed he will need help.
"Some of the really good teams have got two really big strong ruckman and it will be difficult to expect that [a lone hand every week] from Patrick," he said.
"We can't expect Patrick, who is still maturing in terms of kilograms, to do the whole load so we're going to have to bring Tom Bellchambers in, I would have thought, to assist in that situation."
Hille will have scans to confirm the extent of the damage on Monday.
