Cleary was sensationally benched as a gameday decision by father and head coach Ivan after failing to overcome pain and kicking issues from what was later revealed to be a broken toe on his kicking foot.
Despite it seeming apparent that Nathan was going to spend most of the game on the bench as a "break in case of emergency" feature of Ivan's gameplan, the three-time Dally M Halfback of the Year replaced starting half Jack Cogger after just 25 minutes with the game poised evenly at 6-6.
Cleary's shift lasted only ten minutes when his left ankle was crushed by a dangerous hip drop tackle from Knights forward Phoenix Crossland, who was immediately sent off and referred to the NRL judiciary for a hearing this week to determine a potentially heavy sanction.
Penrith medical staff raced onto the field in significant numbers once seeing the significance of the injury on a television replay and were confronted with Cleary's left foot pointing in an unnatural direction.
It became immediately clear that the physios and doctors were dealing with a double compound fracture in Cleary's left ankle, which involves a broken bone piercing the skin.
A compound fracture can cause significant bleeding, which was an immediate concern for medical staff, one of whom described the injury to Nicolussi as like "a bullet wound" due to the profuse bleeding.
Nicolussi said that several Panthers support staff members had to assist paramedics in keeping Cleary's left leg straight in the ambulance to maintain blood supply to his left foot, which underwent emergency surgery due to the nature of the open wound.
Cleary faces a significant stay in hospital as he also requires surgery on a broken toe in his kicking foot, which was to be pushed back until after next weekend's Grand Final should Penrith have qualified.
Whilst the two Clearys are better placed than anyone to know of Nathan's medical and physical capability, the decision to send him to work with the knowledge of a broken toe - a condition that was kept under wraps as a "stress-related issue" for a fortnight - came into question on Sunday night.
"I knew how hard he'd worked and what he put himself through to play today," Ivan said when defending his decision on Sunday night.
“I went and saw him at half-time and saw the whole crew, my family, in there. That was hard and a bit emotional.
"I know he watched the game in the ambulance. Only made him feel worse I think."