Manchester United's defensive problems this season continued after Jonny Evans left Leicester on crutches after Sunday's 5-3 defeat.
The Northern Ireland international, 26, suffered a leg injury when he tried to block a Leonardo Ulloa shot and hobbled off just before half-time.
"I do not know how bad it is, we will have to have a scan on Monday," said United manager Louis van Gaal.
Tyler Blackett also faces suspension after he received a straight red.
The 20-year-old centre-back has played in each of United's league matches, but will be banned for the visit of West Ham on Saturday after committing a professional foul in bringing down Jamie Vardy.
Full-back Luke Shaw has yet to play since his summer signing because of injury, while another recent defensive recruit, Marcos Rojo, did not make his debut appearance until the victory over QPR on 14 September because of work permit issues.
Evans's injury will be a concern for Northern Ireland manager Michael O'Neill ahead of the Euro 2016 qualifier against the Faroe Islands on 11 October.