Morris, who came on as a substitute at half-time, left the game in the 66th minute after landing awkwardly.
Swansea did not give any official details about the injury.
"It does not look good, does it? I don't know the extent of it but we have our fingers crossed for him," Swansea manager Steve Cooper said after the match.
"We will know more in the days to come, but it did not look a good one, that's for sure.
"He will travel back with us, he is currently in a knee brace and on crutches.
"We will get the best attention to him as soon as possible."
Morris, 26, joined Championship club Swansea on loan from the Seattle Sounders in the January transfer window.
He made his Swansea debut in a 3-1 win over Rotherham on Jan. 30.
In better news for the U.S., American midfielder Duane Holmes scored his first two goals since his return to Huddersfield, helping his side to an important win as they seek to avoid relegation from the Championship.