Steve Cooper has revealed Joe Rodon will undergo an operation that will keep him sidelined for the remainder of 2019.
The centre-back suffered two separate ankle problems after the international break but picked up a fresh injury in the 3-0 loss to Brentford last Tuesday.
It ensured he was unable to feature for the Swans in their with his replacement Ben Wilmot scoring what proved to be the winner against the Bluebirds
He will also miss Wales' final two Euro 2020 qualifiers against Azerbaijan and Hungary in November.
And Cooper revealed academy product Rodon was close to tears when he discovered the full extent of his injury.
"First of all I'm disappointed for Joe, he picked up a fresh injury on Tuesday night," said Cooper.
"We were a little bit worried because he had a knock on the ankle last week which he was trying to play through so we thought it was an extension of that. But it’s a new injury that’s ruled him out for a few months. He's going to need an operation next week.
"He's got a tendon injury that rules him out of the Wales games too. We're disappointed for him, but what hurts him will make him stronger.
"He was close to tears. I think it hit home yesterday when he knew he wasn't going to play. But he stood by the side of the team and didn’t leave us for one minute. That’s disappointing for him. But we look forward to welcoming him back and looking after him through his rehab.
"We knew he was touch and go in the press conference because he was swollen, but we were hoping it might have just been another kick.
"But when he got scanned and came back, it was a fresh injury. We knew his fate then, or our fate. Injuries happen, it’s disappointing but we have to get on with it."
Rodon's absence paved the way for Wilmot to make his first league start since joining Swansea on a season-long loan from Watford.
to earn Swansea all three points against bitter rivals Cardiff at the Liberty Stadium.
And Cooper heaped praise on his assistant Mike Marsh for plotting the move that led to Wilmot's matchwinner on the pitches of Swansea's Fairwood training complex.
"For Ben, on the other side of the story, he's a really good player and a good lad. He has had to wait for a start in the league. I know he's played in a few League Cup games," added Cooper.
"He’s had to stay patient and he’s not been happy with it. We’ve had a good few conversations.
"All of the players know that we train in a way that whenever they're called upon, we've made a lot of changes in the last three games, they're ready to play. You saw that today.
"You see the fitness levels and tactical ideas it’s exactly how we want to play because we practice it every day. Ben is a good example of that.
"For him to score, I've got to give Mike Marsh all of the credit. The corner was right off the training ground, Marshy has a brilliant eye for spotting how to score off set plays and it’s come off today."
Victory saw Swansea - who rose to fourth place in the Championship table - end a run of four matches without a win on home soil.
Cooper's men return to action against Wigan Athletic at the DW Stadium this weekend before facing Sheffield Wednesday at Hillsborough seven days later in their final game before the last international break of 2019.
