The Irishman has undergone a cartilage operation which will keep him out of action for at least six weeks.
Daly scored 21 goals as Rangers strolled to the League One title and a place in the Scottish Cup semi-final last season.
The enforced lay-off for the 31-year-old is offset by the arrival at Ibrox of fellow 30-somethings Kris Boyd and Kenny Miller, who joined Ally McCoist's squad last month.
The former Scotland strikers will add to the attacking options along with Nicky Clark and Dean Shiels, who were among those challenging former Dundee United striker Daly for a starting place last season.
"It's a real shame as big Jon was fantastic for us last season," said McCoist. "Towards the end of the season, we would have given him a little rest if we could have but personnel indicated we couldn't.
"With Andy Little injured, he was our only striker at points and to be fair to him, he kept turning up and playing for us. He was playing through a little bit of pain then had a good rest in the close season but there is still a little niggle there.
"We sent Jon for a scan and that showed he has a problem with his cartilage so he has gone back to the same surgeon who did his other knee.
"It looks as though he will be out for six weeks and it's a blow for the team. It's obviously a blow for him too but the bottom line is he has to get it sorted as quickly as possible."
Watch Rangers kick off their Championship campaign against fellow new-boys Hearts at Ibrox on Sunday, August 10 on Sky Sports