Slater knew there was nothing he could say to make everything better when he sat with Munster in his room at Queensland camp on Sunday, the day the new Maroons captain learned of his father Steven's sudden death.
Munster vowed then and there to Slater that, after spending some time with his family, he would lead Queensland in Wednesday's Origin decider - one of the biggest games of his career.
"He didn't have a lot of answers for a lot of other things, but he gave that one to me pretty straight," Slater said.
"It's a huge game and he wants to be a part of that."
To give him as much time as possible with his family, the Maroons booked Munster on a separate flight that would get him to Sydney in time for Tuesday afternoon's captain's run at Accor Stadium.
"I can't wait to give him a hug," Slater said ahead of Munster's reunion with the team.
"Naturally, he's been pretty upset over the last couple of days, but I think the last couple of days he's been where he's needed to be, and that's with his mum and his sister."
Slater understood the best thing he could do for Munster sitting in his room on Sunday was to be there as a mate, and give him all the time he needed with family.
The coach knew that because he lost his own father Ronnie earlier this year.
"There's no real words that fix any of this," Slater said.
"Unfortunately there's not a switch (to flick).
"I haven't dealt with this as a coach, but I've dealt with it as a person. I lost my father in January. I know what it's like and Cam's an inspiration for many people.
"He's a hero to many people in Queensland. I can only imagine his dad would've been his first inspiration and his first hero. He'd be hurting right now."
That's why Slater knows Wednesday night is the time for the Maroons to show up for Munster, just as he showed up for his teammates guiding them to victory against the odds in Origin II.
"Their skipper is going to need them on Wednesday night," Slater said.
"I'm sure it'll give them a huge boost, to see their mate going through something that you only go through once in your life, losing your father. I'm sure it's going to have a huge impact on them."
Slater has already seen his senior players leading the group with aplomb in Munster's absence.
It's been a blessing for the group to have Josh Papalii, the Canberra prop called out of representative retirement to reinvigorate the forward pack.
"It's a feel, with 'Papa'," Slater said of the veteran's impact on the squad.
"The best way I could describe it is it's probably a calmness. Big Tino (Fa'asuamaleaui) has been like a little puppy dog, following him around all week."
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