An emotional Crossland agonisingly watched the replay looping on the stadium big screens as Cleary was given the green whistle and taken off by medicab en route to hospital.
The hooker looked on the brink of tears when he was summoned to hear his punishment from referee Gerard Sutton.
"Initially he's up high, makes a definite action to twist and comes down on the leg with weight, there's extreme risk of serious injury, you're off," Sutton told Crossland and Knights captain Kalyn Ponga.
It's the first send-off for a hip-drop tackle in NRL history, after they were outlawed in 2020.
The longest ban handed down for a hip-drop tackle is five matches, given to both Jeremiah Nanai in 2023 and Josh McGuire in 2021.
The only way Crossland could avoid a ban is if he was handed a grade-one charge, but given injuries are taken into account that appears almost certainly out of the question.
Harrison Graham, who has become a regular off the interchange for the Knights this year, looms as the most logical replacement for Crossland.
The Knights No. 9 will learn his fate when the match review committee reveals the judiciary charges on Monday morning.
"He was disappointed, we've got to try and get him upbeat," said Knights coach Justin Holbrook.
"He's an emotional guy. He's been so great for us every week this year. Hopefully Nathan's okay."
Any ban for Crossland would also extend into the World Cup, and threaten to rule the New Zealand hooker out of part of the tournament.
Cleary's injury was later confirmed to be a compound fracture and dislocation of the left ankle.
The send-off reduced Newcastle to 12 men for the remaining 45 minutes of the contest.
The tackle silenced the packed Accor Stadium crowd, as Cleary's foot stuck out an unnatural angle and had to be held in place while he left the field.
"It shouldn't be at that angle. You can see the reaction of the players, they heard a crack," Andrew Johns said on the Nine Network.
"It's a sad sight, you wouldn't wish this on any player at anytime, but (certainly not) to our game's champion player," co-commentator Phil Gould added.
The Penrith fans in the crowd, although outnumbered by blue and red, let out cheers when the send-off was announced.
During a 2022 NRL preliminary final, South Sydney winger Taane Milne was sent off for a wild high tackle on Penrith's Spencer Leniu, at the time becoming the first player to be sent off in an NRL finals match since 1994.
