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.
“He’ll be back with us next week. It’s a blow, it’s disappointing, but it’s part of the game and hopefully he won’t be too long. He’ll come back strong, fit and fresh.”
Carrick said he would “have to wait and see” on the fitness of Morris’ midfield-partner Hayden Hackney, who is nursing an ankle problem.
“We’re hopeful, we’re not giving up on him,” Carrick said, with reference to Saturday.
Left-back Lukas Engel and centre-back Rav van den Berg have resumed light training after injury but remain absent, having missed 12 and three games respectively.