Michael Carrick admits the loss of midfielder Aidan Morris for "a number of weeks" is a blow for Middlesbrough.
The 23-year-old USA international suffered a twisted knee in training with his country ahead of their Concacaf Nations League quarter-final against Jamaica.
Morris had played all 21 matches for club and country since the start of the season, having appeared in 22 more for previous club Columbus Crew between February and June.
Carrick has given his blessing for Morris to remain in the US before linking up with the Boro squad next week.
"We’ve given him an extra little bit of time off because it’s the right thing to do - he’s played a lot of football," Carrick said before his side head to Oxford United in the Championship on Saturday.