Kelvin Langmead will miss three months of action after it was confirmed the Cobblers club captain has undergone knee surgery.
The centre-back had an exploratory operation on Thursday and the result of the diagnosis is that he will be unavailable until mid-October.
The news is a significant blow to manager Aidy Boothroyd, who has lost Clarke Carlisle to retirement this summer and seen Nathan Cameron reject terms at Sixfields to sign for Bury.
“Kelvin has got a microfracture on the inside of his knee and when he had his knee opened up there was some cartilage floating around in there,” he said.
“It’s better that he gets it sorted out and he can move forward - from that point of view he’s happy.”
Boothroyd currently has veteran defender Darren Purse on trial at Sixfields but is reasonably content with his options to replace Langmead, with Lee Collins and Ben Tozer playing there for 90 minutes against Peterborough on Saturday.
The manager also feels an element of regret that Langmead was rushed back into action at the tail end of last season after initially picking up the injury in the win over Oxford on Match 23.
“I don’t think we’d have done anything differently last season; maybe with hindsight we’d have been better letting him come back at his own pace,” said Boothroyd of last season’s player of the year.
“We had a conversation and we agreed we would push it to get him ready for the run-in and the final and this is the risk you take when people come back when they’re not ready.”
With Langmead missing, the club could kick off the campaign at York City without three first-team regulars after it was also confirmed that striker Clive Platt and winger Chris Hackett will not be fit for the start of the season.
But Roy O’Donovan, who sat out Saturday’s game, will be, with Boothroyd confirming the Irish forward missed out as a precaution.
“With the grounds as hard as they are and the weather the way it has been, it’s probably not a good idea to whip them,” he said.