The versatile defender, whom Postecoglou had identified as ideal for his expansive system even before officially taking charge, will be a significant absence.

Aina's ability to drive forward from the back, provide width, and maintain composure in possession made him a perfect fit for Postecoglou's trademark style.

His absence now forces the new manager to reconsider both defensive arrangements and attacking transitions as Forest prepare for their next fixture.

Despite the setback, fans will still get a first taste of Postecoglou's philosophy on Wednesday when Forest face Swansea City.

The match represents an opportunity to begin implementing his dynamic, high-tempo approach ahead of the Europa League campaign.

Postecoglou hinted at tactical changes immediately after the weekend clash with Arsenal, signalling his intent to reshape the team around pace, width, and constant attacking movement. Swansea provides a timely platform for testing these ideas in a competitive setting.

"I was looking forward to working with him," Postecoglou told BBC Radio Nottingham.

"I watched him as an opponent last year and, particularly with the way I like my full-backs to play, he was a perfect fit for it."

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