Cobblers defender Sid Nelson is set to be out for the 'very long term' after confirmation he has suffered an ACL injury.
The 25-year-old centre-back sustained the injury in training last week and went for surgery on Monday when the extent of the problem was confirmed.
No timescale has been put on his recovery but it seems highly unlikely that Nelson will play again this season.
"The update is that he's got an ACL tear and a meniscus tear as well so it's going to be a very long term injury for Sid," said manager Jon Brady.
"We'll support him in every way we can on that because it's heartbreaking for him and for Joseph Mills as well.
"Not only are they fantastic characters around the building, they're also just great guys and you don't want to see anyone go through that, especially these young footballers."
Another player to suffer a serious-looking injury was Scot Bennett during Tuesday's game between Newport and Northampton at Rodney Parade.
The Exiles defender appeared to land awkwardly and needed to be stretchered from the field.
"I made sure I gave Scot Bennett a call after his injury for Newport because I wanted to wish him all the best," Brady added.
"These are young guys doing what they love and trying to do their best for their team and you don't want to see that on a football pitch for any player."