Jordan Morris' European adventure has already ground to a halt.
It's yet to be determined if Morris will rehab with the Championship club or back in the U.S.
"He has had a bad injury, unfortunately, there's significant ligament damage, (to his) ACL," Swans manager Steve Cooper confirmed on Monday. "Everything we hoped it wasn't, it has turned out to be.
"It's the end of his season with us and a long road back to recovery for him."
Morris moved to the promotion-chasing Welsh club in January for his first chance to prove his quality in Europe. He had attracted interest from clubs in the Premier League, Bundesliga, Serie A, and Ligue 1 for his performances with the Sounders and USMNT over the previous two years, according to The Athletic's Stuart James.
The 26-year-old made three substitute outings in the Championship and started an FA Cup bout against Manchester City before being named in the Swans' starting XI for Saturday's trip to Huddersfield Town. He landed awkwardly after treading on the ball and was stretchered off after little over 20 minutes.
The injury represents a significant setback in both Morris' club and international career. The forward is almost certainly ruled out of the USMNT's Gold Cup campaign which kicks off this summer.