So much so the famously stoic Panthers boss needed a moment to collect himself after the younger Cleary aggravated a shoulder injury in the loss to Melbourne last Thursday.
Scans have since revealed Nathan Cleary will need until week one of the finals to rest his injury, which had appeared to threaten Penrith's historic push for a fourth consecutive premiership.
"He's obviously disappointed but the scans definitely could have been worse. There's obviously some hope there," Ivan Cleary said.
Cleary has named Brad Schneider to partner Jarome Luai in the halves against Canberra this week for the first of three games until his son's expected return date.
But Jack Cole has been included on the bench and, like Schneider, filled in for Cleary during the halfback's hamstring issues earlier this season.
Coach Cleary indicated he may wait until the 11th hour to finalise which of the pair comes into the starting side, with both also capable of playing from the bench as a utility.
"We're playing Saturday. We've got a bit to go yet," he said.
Cleary is content to take an adaptable approach, given the Panthers have become used to rolling with the punches during a season when only one man - Lindsay Smith - has played every game.
Penrith's 14 premiership players have been unavailable for a total of 59 matches between them through 24 rounds this season.
"It's been quite a disruptive year for us as a team," coach Cleary said.
"We've had guys coming in and out whether it's through injury or suspension or Origin all year pretty much. I guess we're used to it.
"We're basically ready for it, no matter what happens for the rest of the year."
Nathan Cleary clutches at his shoulder during the loss to Melbourne. (Mark Evans/AAP PHOTOS)
But while Cleary the coach has felt equipped to adapt on the fly, handling his son's injury struggles has tested him as a father.
He made a bee-line for the sheds when Nathan aggravated a shoulder injury initially suffered in the lead-up to the World Club Challenge.
Normally the separation of powers is easy for Cleary, and no doubt assisted by the fact his son is generally regarded as the best player in the NRL.
But on Thursday night, when his coaching brain wanted to focus on the next three weeks and the Panthers' push to lock up second place on the ladder, Cleary found himself feeling for his son.
"It's not that easy," he said.
"Certainly on the weekend, I guess there was a cross between understanding the relevance to the team and where we are in the season, (but) also as his dad just knowing how shattered he'd be.
"There was a moment there where I had to get myself back in the present and focus on what I was doing. It's hard.
"Injuries are definitely hard. Just playing and that, it's pretty easy to separate (being father and coach) but I don't think you can separate it in that sense (injuries)."
Luke Sommerton will start at hooker for the trip to Canberra in place of Mitch Kenny, who received a one-game suspension for his high shot on Storm winger Grant Anderson.
Mavrik Geyer holds his place in the second row ahead of Scott Sorensen, who is expected back from his hamstring injury in time for finals.
