Fremantle ruckman Jon Griffin "tweaked his groin" in the final on-ground warm-up and was withdrawn 10 minutes before the opening bounce, with Sandilands included to play a key role in his team's 22-point win.
There was speculation on Saturday morning that Sandilands would play his first game in more than two months, with the 2009 club champion named as an emergency.
Asked if he thought Sandilands was always going to play on Saturday, Hardwick said: "Look, that's within the rules. Whether it's in the spirit of the game, I don't know. That's for you guys (media) to find out".
Hardwick was then asked whether he thought Griffin's injury was genuine.
"I think everyone knows the answer to that question in here. Listen, you guys take that further, I've said enough on that," he said.
"You prepare one way and then all of a sudden, something happens and you've got to start preparing another way."
Lyon's response was emphatic on Saturday night. He challenged anyone doubting the legitimacy of Griffin's injury to provide evidence.
"I'm on record here, this is bona fide and legitimate, and if anyone wants [to make] accusations outside of that they're well and truly out of line and want to be really careful," he said.
"There is no ruse here. If anyone is calling us liars, they'd want to be really strong and have strong evidence."
Asked if he would speak to Hardwick to clear the air, Lyon said: "What for? Not interested. He’s a really good person, a really good coach, but we take the four points and move on".
Lyon said Griffin told him he wasn't "confident to play" after tweaking an adductor in the warm-up and Sandilands, who had been completing his own warm-up inside, was called on two minutes before the team ran onto the ground.
"I called [the players] over into a group - that'll be on camera - and I said, 'I don't want to shock you but Aaron's in and Jon's out'," Lyon said.
"When I spoke to Aaron, Aaron didn't even know who had gone out of the team.
"I understand what people think, but the reality is, I can't put it any clearer ... we always warm up our emergencies."
Sandilands hadn't played at AFL level since round 11, but he returned to have 33 hit-outs and nine clearances in a strong performance, giving his team a midfield edge.
It was enough to convince Lyon that Griffin, who will be assessed, could struggle to get back in the team for next Sunday's crunch game against North Melbourne at Etihad Stadium.
"When you give your spot up it’s hard to get back in, which is good for me but bad for Jon and great for Aaron," Lyon said.
"It’s really difficult to play both. Aaron’s performed and (Kepler) Bradley’s performed. It’s a tough ruthless business ... but we can’t delve into how people feel, it’s how they act."
Nathan Schmook covers Fremantle news for AFL.com.au. Follow him on Twitter: @AFL_Nathan
