Tatola's first run of the game saw him remain on the ground, and then be tended to by South Sydney's trainer in back play as the game continued.
The prop was ultimately able to play out his first stint in the 50 points to 16 thrashing, with that lasting 29 minutes.
It was a strong return for the prop too, with his go-forward making a substantial difference to South Sydney, but the coach said it was all part of the plan for Tatola to never return for a second stint, while suggesting his knee concern came from a hip drop tackle.
"He's fine. That was the plan all along," Demetriou said on Tatola.
"He probably came back a week earlier than we expected. The medical staff and Junior were really keen to do that.
"He probably had a bit of a hip drop earlier and it probably scared him more than anything.
"He was really keen to go back on in the second half, but I said to him all week that if we didn't to then I wasn't going to put him back on. He will be fine by next week."
Demetriou said Thompson will have to have scans to ascertain the extent of the damage.
"He will have to get some x-rays, go for some scans. Fingers crossed he isn't too bad, but we will have to wait and see," Demetriou said.
While Bulldogs' coach Cameron Ciraldo reserved judgement on the tackle and said he would have to watch it again before commenting, Demetriou said there could have been at least four hip drops during the game.
He implored clubs to take the tactic out of the game, given it wouldn't be practised at training.
"I think there was a few hip drops. I think there was at least four of them during the game," Demetriou added.
"We keep saying that it's not a problem in the game, but if that tackle happens on the training field, I can guarantee your teammates aren't happy about it. I don't know why if we aren't doing it at training, why we are doing it on the field.
"I get there are circumstances where it's an accident, where there is some swing in the tackle, I understand that.
"But when you are side by side and you lose your legs to drop your hips down, it's not a way to take people to ground. It's a lazy way. I think the game is doing a great job doing what they can, but it's up to the clubs to show some onus on it.
"It's going to effect your team somewhere. You're going to lose a high-quality player somewhere. We don't practice it at training. I don't know why we are accepting that's okay on the field."