Jones (18) picked up the injury during the Carabao Cup tie at home to Plymouth last month. He is still wearing a leg brace and faces another two months on the sidelines.
“Ricky is young and strong so he will come back from this, but the injury was as serious as it could get,” Ferguson admitted. “It’s a big shame for him and for us because he was looking good. He’ll be out for another two months and we won’t be rushing him back. We will need to make sure he is ready.
“We are now left with three strikers in Siriki Dembele, Jonson Clarke-Harris and Jack Marriott, none of whom have been fully fit all season, but the international break will give us the chance to get some one-on-one work into them to improve their sharpness.”
Ferguson also delivered an update on the fitness of captain Mark Beevers. He is currently sidelined with a hamstring injury and won’t return until after the second international break which covers the weekend of October 9/10.
“Sometimes you don’t realise how important a player is until he’s not around,” Ferguson added. “And that’s the case with Mark. We’ve missed his left foot, his height and his experience, particularly in the Championship. We’ve also missed his personality. He’s keeping his fitness up on the bike which obviously isn’t the same as working on the grass, but again we won’t be taking any risks with him.
“We are lucky the time he will be out injured covers both the international breaks.”
Beevers suffered his injury when Posh were 2-0 up against Cardiff in a Championship fixture at London Road last month. Posh drew that game 2-2.