Manchester City manager Roberto Mancini admits he made a mistake by failing to boost his defensive resources in the January transfer window.
The champions have been without influential captain Vincent Kompany since the centre-back suffered a calf injury at the end of January.
There was still time to bring in cover but Mancini decided against it, something he now regrets.
"Probably we made a mistake because when we knew of this problem we were four days to the close of the market," said the Italian.
"Probably then we should maybe have bought another defender.
"Also, last year he had this problem, for one month he didn't play. This is a big problem. For me we made a mistake in this case.
"We had a chance because we had one good defender (in mind) but we didn't think that Vinny would stay out for 40-45 days."
Kompany, 26, suffered the injury in the FA Cup win at Stoke on January 26 and has been out ever since.
Although he has started running again, he is unlikely to be fully fit until after next week's international break.
City didn't expect him to need such a long lay-off and their form has plummeted in his absence.
City trailed neighbours Manchester United by just five points before Kompany's injury but have now dropped to 12 points off the pace, and with little chance realistically of defending their title.