The Japanese forward went down after off-the-ball tussles with Hearts defenders on a number of occasions in Celtic's 3-2 Premier Sports Cup win, before Craig Halkett was booked for another incident that was spotted by an assistant referee.
The pacey striker got up and urged the crowd on as if to show he could get off the ground and fight back, and the response was no surprise to former Yokohama Marinos boss Postecoglou.
Furuhashi had the last laugh by netting his fifth goal in four starts for Celtic to put them 3-1 ahead in the second half.
"I'm sure he's had that in his career in the past," Postecoglou said.
"I think he can handle himself all right. You saw that he just gets on with it. If the opposition resort to those sorts of things to try and stop him then that just shows how much of a threat he is.
"He's the type of player supporters want to watch and he feeds off their energy."
The recent arrival started on the left after injuries to Ryan Christie and Liel Abada led to Odsonne Edouard being recalled at centre-forward, but he adapted brilliantly and had a hand in the other two goals while remaining a goal threat himself.
"He's a smart player, he is intelligent," the Celtic manager said. "We played him out on the left but I knew he could handle it all right. He's always a threat and is super positive in himself.
"He took his goal well and his pass to James Forrest for the first goal was just brilliant too. Then again, there is more to come from him when he settles."
The former Australia head coach added: "If you look at our goals, they have been shared through everyone that has played on the front line.
"James Forrest has scored, Liel Abada has got goals, Kyogo has got goals.
"If we play the football we can play then whoever plays in that front three will get goals."
The final score did not reflect Celtic's dominance. Carl Starfelt gifted Hearts their first goal after being caught in possession before giving away a penalty which Liam Boyce netted.
Celtic's intensity dropped in the final quarter as Postecoglou brought on four substitutes including debutant James McCarthy, and Aaron McEneff netted for Hearts in the dying seconds.
Postecoglou was not too concerned about the Hearts goals given his side's dominance in the opening hour or so and he hopes the lapses are reduced when he gets more players in.
"It doesn't have to happen," he said. "I keep saying it, we need more players to support the ones we have.
"Some of them are putting in enormous shifts with some playing 90 minutes every game and others playing 70 minutes and putting in a power of work."