Hawthorn assistant coach Brett Ratten has farewelled his son Cooper, 16, with a public letter, saying his memories will last forever.

The teenager was killed in a car accident at Yarra Glen, north-east of Melbourne at 3am on Sunday.

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The 255-game star – who played in Carlton’s 1995 premiership – and ex-Blues’ coach revealed the extent of his heartache.

“We love you so much and we will miss you forever. You will be with us every minute of every day,” Ratten wrote in the letter published by News Corp.

“You had so much potential and ability in the things you set your mind to. You have been taken way too soon and we will miss your smile, your laugh and all your cheekiness.

“These memories will last forever. I wish I could kiss you, hug you and hold you tight. I love you, my son. We love you so much always and forever.”

The teenager driving the car was released from hospital and police custody on Sunday. The Healesville boy sustained minor injuries.

The passenger in the car, 17, is still in hospital in a serious condition.

According to reports, Cooper allegedly wasn’t wearing a seatbelt in the back seat of the VW Tiguan when it crashed.

The three teenagers had been at a Yarra Glen Football Club function before the crash. Police said the conditions were foggy and the car may have belonged to one of the parents.

Police said it was a “miracle” the two other boys survived.