Sir Alex Ferguson has revealed that Rio Ferdinand is likely to be sidelined for six weeks with a hamstring injury.
The England international picked up the knock during Manchester United's 2-1 victory over West Bromwich Albion on Sunday.
He limped out of the action after 75 minutes and was clearly in some discomfort.
Ferguson had already seen Brazilian full-back Rafael ruled out before the game with a dislocated shoulder, while captain Nemanja Vidic also limped off against the Baggies.
He is now facing something of a selection poser at the back, but he is confident United have the strength in depth to handle an early-season injury crisis.
"We have had a torrid two or three days because young Rafa has done his shoulder in training on Friday, he will be out for 10 weeks because he needs an operation," Ferguson told Sky Sports.
"Rio will be six weeks. Vida, we don't know if it is a nerve or not and we will have that checked tomorrow (Monday). He could be out for a couple of weeks.
"But with having Phil Jones, Chris Smalling and Jonny Evans, it's a god send to be honest. Patrice Evra will be back next week, so we have got options."
United went in front at the Hawthorns through Wayne Rooney but required a late own goal from Steven Reid to secure the points after Shane Long had forced a low drive under David de Gea.
On the performance put in by his side in the Midlands, Ferguson said: "The first 25 minutes, I thought we were superb. Our movement of the ball was great and the interchange of play. The speed of the play was great and then for some reason we slowed the build-up to a level that we lost our momentum.
"We then lost a goal that David should have done better at - I think it was just a lack of concentration, but welcome to English football. He took a battering in the second half and should have been protected more by the referee, but he wasn't. He has had to withstand it, so it's a good experience for him."
De Gea also experienced a tough time in United's Community Shield victory over Manchester City, but Ferguson is confident the young Spaniard will learn from his mistakes.
"I think my recollection of goalkeepers coming from Europe is that it is a learning process," he said.
"We expect a learning process to be in operation and we will see it through. We just need to pat him on the head."