Spurs have enjoyed an encouraging start to the season under the Australian, going unbeaten in their first four Premier League games ahead of Saturday’s clash at home to Sheffield United.
For all of their attacking enterprise, however, they have twice conceded two goals in a game, against Brentford and Burnley.
The club spent around £43m to sign Micky van de Ven and the Dutchman has impressed alongside a reenergised Cristian Romero but convincing options behind the pair are light.
Eric Dier has not been involved while Davinson Sanchez was sold to Galatasaray, meaning the club will look to put their faith in teenager Ashley Phillips, who joined for £3m from Blackburn earlier this summer.
Ben Davies is another option in central defence but Postecoglou has confirmed the club “need” another centre-back, though whether that comes in January remains to be seen.
“We are a little bit light there but, for Davinson, it was a good opportunity to get a long-term contract,” he said.
"We needed to rebuild the squad - there was no point tinkering around the edges.
"We still probably need another centre-back."
The Spurs boss added that Dier and former club captain Hugo Lloris, who did not leave the club despite wanting to, are still training with the first-team squad.
“It was a fairly fluid situation. We weren’t really sure what was going to happen with Hugo.
"Once we got to the end of the window, we knew the numbers we had.
"They were training before with the first team and they are now."