Manchester United's injury crisis deepened on Thursday when coach Sir Alex Ferguson revealed that centre-back Rio Ferdinand may miss the rest of the season with a calf injury.
The England captain sustained the injury in the warm-up ahead of United's Premier League defeat at Wolves on February 5 but was expected to be able to play some part in the title run-in.
"Rio has been out for a few weeks now," said Ferguson.
"We are not looking at this as a short-term situation. He has not started training yet. We will be lucky to get him back for some part of the season."
Ferdinand's regular partner in central defence, Nemanja Vidic, missed the 2-1 defeat of Marseille in the Champions League on Tuesday and Ferguson confirmed that he would also miss Saturday's visit of Bolton.
"Vidic won't make it," confirmed Ferguson.
"He is showing good recovery for this week and should be OK after the international break but not enough for Saturday."
There has been further bad news for United in the defensive sector, with John O'Shea ruled out for five weeks with a hamstring injury sustained against Marseille at Old Trafford.
O'Shea's replacement against the French champions, Rafael, also limped off later in the game and Ferguson said the Brazilian right-back would be out for "two to three weeks".
The injury glut leaves Ferguson with just four fit senior defenders - Fabio, Chris Smalling, Wes Brown and Patrice Evra.
It may prompt a return for Northern Irish international Jonny Evans, who has not featured since standing in for Ferdinand against Wolves after collecting an ankle injury in training.
"It has been a bad spell for us," said Ferguson.
"Only a few weeks ago we had every defender fit and things were looking great. It has all just fallen apart in the last week or so.
"Hopefully Jonny Evans may be fit for Saturday, even if it is a bit of a risk. He has trained all week but he has been out for such a long time."
Meanwhile, Ferguson expressed his shock at being handed a five-game touchline ban for comments about referee Martin Atkinson in the aftermath of United's 2-1 loss at Chelsea earlier this month.
The Scot has yet to decide whether to appeal against the suspension from the Football Association but he expressed shock at the weight of the punishment.
"It is disappointing," he said.
"It is the only industry where you can't tell the truth. But it is in the past now."