The incident occurred with just under 20 minutes left to play at the King Power Stadium as Bentancur clashed heads with Leicester's Abdul Fatawu as he looked to attack a corner, and fell straight to the ground.
Bentancur, 27, was initially unresponsive as he lay on the pitch, sparking concern from both sets of players as medics rushed on to aid the Uruguayan.
Following over seven minutes of treatment, Bentancur eventually sat up but required oxygen before being stretchered off and he did not return to the action as Postecoglou made a quadruple substitution. Speaking after the match, the Australian manager revealed that Bentancur was 'up and talking' but was clearly still concerned for his player after the sickening clash of heads.
'We've got to be very careful,' Postecoglou said. 'The good news is he was up and talking. We'll let the medical team take care of that.
Rodrigo Bentancur was knocked out cold after a clash of heads, leaving both sets of players visibly concerned
Ange Postecoglou revealed Bentancur was talking after the game, but admitted he needs to be 'very careful' with the midfielder following his worrying head injury
'I don't have a lot of information but I know he is up and he's communicating so he's fine from that point of view.
'But obviously a head injury and I'll leave it in the hands of medical team now. The key thing is that he's definitely conscious and communicating.
'Whenever it's a head injury and you see a player go down, I think nowadays we're always cautious in that moment and I don't know the actual circumstances but I know it was a head collision.'
Bentancur does not have fond memories of the King Power Stadium, having ruptured his ACL at the same stadium during a league match in February 2023 that ruled him out for eight months.
He will hope that this is a far less severe setback, but now faces a race against time to return for Spurs' next league game at home to Everton on Saturday afternoon.
The midfielder will need to pass concussion tests before returning to Postecoglou's matchday squad, and Tottenham face a quick turnaround in between games.
In Bentancur's absence, Tottenham were unable to find a winning goal as they failed to begin their campaign with a victory against their newly-promoted opponents.
Pedro Porro gave the visitors the lead in the first half after heading home James Maddison's cross, but Tottenham failed to make the most of their dominance and were pegged back after the break when Jamie Vardy scored from close range to earn the Foxes a point.