Defender Rio Ferdinand will miss Manchester United's Champions League football quarter-final first leg against Porto at Old Trafford tomorrow after failing to recover from a groin injury.
The problem forced the England centre back to sit out the dramatic 3-2 home win over Aston Villa in the Premier League, a match where United's defensive unit looked unusually vulnerable.
With Ferguson wary of the threat posed by Porto and their powerful Brazilian striker Hulk, he admitted there needed to be a big defensive improvement if his side are to take a commanding advantage into the return leg in Portugal.
The holders will be boosted by the return from domestic suspension of Nemanja Vidic, Paul Scholes and Wayne Rooney, who all missed the Villa game which was decided by teenage substitute Federico Macheda's stoppage-time winner.
The 17-year-old's reward for his dream debut was a place among the substitutes for tomorrow's match at Old Trafford.