Alex Ferguson has received some welcome relief amid a defensive injury crisis after initial examinations suggested Rio Ferdinand did not suffer major damage to his groin in Manchester United's FA Cup semi-final.

The England defender limped off during the first-half of Saturday's 4-1 win over Watford, adding to an injury list that already included Gary Neville, Nemanja Vidic, Mikael Silvestre and John O'Shea.

Immediately after the game, Ferdinand expressed the hope he would not be out too long and it appears those wishes will be granted.

While a return against Middlesbrough on Saturday is far more likely, Ferguson has not entirely given up hope of Ferdinand being involved against Sheffield United at Old Trafford tomorrow when United will look to extend their lead at the Premiership summit to six points.

The same is also true of John O'Shea, who sat out Saturday's victory with a minor calf injury. Should neither Ferdinand nor O'Shea make tomorrow's game, Ferguson will face a dilemma over who should fill the right-back slot.

Darren Fletcher is favourite to retain the role after doing well as an emergency replacement for Ferdinand in a back four which saw Gabriel Heinze partner Wes Brown in the middle.

The only other plausible option is to hand 18-year-old Northern Irishman Craig Cathcart his debut. Normally a central defender, Cathcart has impressed and reserve-team and academy level this term and been a key figure in United's run to the Youth Cup final.