Manchester United midfielder Nemanja Matic is reportedly a doubt for his team's trip to Chelsea this weekend.
Matic withdrew from the Serbia squad for their UEFA Nations League double-header against Montenegro and Romania after picking up a back problem.
The 30-year-old has been undergoing treatment at United's Carrington training base, but according to Sky Sports News, he is far from certain of being available for the clash at Stamford Bridge.
Matic - a 2017 arrival from Chelsea - has already made eight appearances for United this season despite missing the start of the campaign following surgery on an abdominal problem.
United currently sit eighth in the Premier League table ahead of Saturday's trip to Chelsea, who sit second in the division, level on points with leaders Manchester City and third-placed Liverpool.