The 21-year-old Perth-born midfielder had been enjoying an excellent loan spell with the English League Two club before coming off second-best in a challenge in Tuesday's 3-1 loss to Notts County.

Lincoln physio Michael Wait said: "He picked up the injury in a tackle and the initial prognosis is not good with the injury looking quite bad.

"He has returned to Villa this morning (on Wednesday) where he will have a scan and be assessed by their medical team."

Herd, who was in the Australia squad for the Under-20 World Cup in Egypt last year, had scored four goals for the Imps during a 19-game spell in Lincoln.

It is understood Lincoln City were impressed with the energetic Herd and are hopeful of persuading him to sign a permanent deal, although the Aussie may sign a one-year contract extension with Villa in a crucial 12 months for him.