Villa forward Emiliano Buendia and defender Tyrone Mings are also sidelined with ACL problems.

"When they are injured for a long time, it's the worst in football," said Emery.

"It's more difficult for the player, as a person, when they are injured.

"We've had two injuries for a long time, for all the season, with Buendia and Mings.

"Now it's the same for Kamara. Maybe, more or less, in September or October he is coming back."

Defender Diego Carlos will be out of action for up to four weeks because of a hamstring injury suffered in training this week.

Villa, who are fifth in the table, travel to Fulham on Saturday.