Manchester United are uncertain whether to extend Edinson Cavani's contract amid concerns over his availability.

The Manchester Evening News can reveal United staff are frustrated with Cavani's recent lay-off with a muscular injury as medical staff had cleared him to play in some games.

Cavani, 34, returned after a 17-day lay-off at Crystal Palace last week but was substituted after 74 minutes and he has missed six of the last seven United games and is not expected to return against West Ham on Sunday.

United manager Ole Gunnar Solskjaer claimed Cavani 'didn't feel right' during United's final training session prior to Sunday's derby at City and the Uruguayan had to cut short his session. Luke Shaw overcame a dead leg to play the full duration of United's victory at The Etihad Stadium.

United have the option of an additional year on Cavani's contract but both parties have to agree to the extension. Solskjaer has previously sounded optimistic about the possibility of Cavani staying beyond the summer and staff at United's Carrington training complex have been in awe of Cavani's presence.