Spurs defender Micky van de Ven has revealed he "was completely surprised by" the club's move to dismiss ex-boss Postecoglou.
Postecoglou's spell in charge was terminated a mere 16 days after he guided the team to victory in the Europa League final, delivering the club's first major trophy in nearly two decades.
Yet, this continental triumph was not matched in the domestic league, with the side finishing in a disappointing 17th position in Postecoglou's final campaign in charge.
He was replaced by former Brentford boss Frank during the summer, but Tottenham currently sit 11th in the table, with 22 points, following a 3-0 defeat to Nottingham Forest at the weekend.
"He was a fantastic manager. I have a lot of respect for him," the Dutch defender stated on The Overlap podcast.
"I don't know how everything went behind the scenes. I didn't expect it. It was odd how everything went after - he's the manager that brought a trophy to the club," he continued.
"Later, when he was dismissed, I texted to my dad and my mates and said, 'I never expected this.'"
Postecoglou arrived at Spurs from Celtic before the 2023/24 campaign, replacing Antonio Conte. He enjoyed early success with his attacking style of play, collecting 26 points from his first ten league matches.
Nevertheless, that unbeaten run was halted with four losses in five games, and the club's season tailed off, eventually missing out on a top-four finish by a mere two points.
In the next campaign, they managed only 11 out of 38 Premier League fixtures.
While he appreciated Postecoglou's style, Dutch international Van de Ven believes the squad was missing a "plan B" and disclosed he and fellow centre-back Cristian Romero spoke about adopting a more cautious style with the manager.
"I liked the offensive play under Postecoglou but I like what we have now with Thomas Frank. We are more secure at the back. I don't like getting exposed every game on the counter-attack," he said.
"At the beginning under Postecoglou, no team was accustomed to playing against our system. We were playing unbelievable football."
"But, managers study everything and people figured out what we were doing. Sometimes we lacked a backup plan and we were getting exposed. We lacked answers to resolve it."
"On one occasion Romero and I approached the manager and said we should change some things and be more defensive to make sure we win those games. He was like, 'I agree with you but I expect you two guys to handle this on the pitch, make sure everybody knows.'"
A seasoned betting analyst with over a decade of experience in sports wagering and financial risk management.