Southend defender Julian Bennett has been ruled out for around six months having ruptured his anterior cruciate ligament in Tuesday's Capital One Cup defeat to Yeovil.
Bennett, who only signed for the club last week after a successful trial, was making his Shrimpers debut in the 1-0 loss but was forced off on the hour mark.
Scans on Wednesday highlighted the extent of the injury and Bennett is now set for surgery before starting his lengthy rehabilitation.
Boss Phil Brown told the club's official website: "It's desperately bad luck for Julian and we're all gutted for him. We'll support him all the way.
"It's football isn't it, sometimes it can be very cruel. We're very disappointed to have lost him to injury for such a long time because he was just beginning to settle at the club.
"He could be out for six months or longer, we don't know yet, he'll have his surgery on Saturday we hope.
"It's not a recurring injury, he had similar on his other leg, but he's not had this injury before.
"It must have come from the way he's landed as he's gone over but Ben Clarkson immediately said he couldn't continue and the scan revealed the extent of the injury.
"We'll support him as a club and hopefully he'll be back quicker than expected."