Manchester United duo Wayne Rooney and Nemanja Vidic both sat out training this morning.
The absence of the key pair from the session at Carrington casts doubts about their availability for the Champions League semi-final against Barcelona at the Old Trafford tomorrow.
Rooney took a knock to his hip before scoring the equaliser in the 2-1 defeat by Chelsea while Vidic suffered a facial injury.
United are aiming to book a place in the final in Moscow after a 0-0 draw at the Nou Camp.
A four-man group comprising Rio Ferdinand, Owen Hargreaves, Michael Carrick and Wes Brown trained away for the rest of the squad at the beginning of the session.
With United looking to book a place in the final, they will be banking on Rooney to recover on time.
The England striker took his tally for the season to 18 goals at Stamford Bridge.
Serbian centre-back Vidic, who missed the first leg because of a stomach infection, saw just eight minutes of action against Chelsea.
He was stretchered off after taking a knee in the face following a tussle with Didier Drogba.