Manchester City boss Roberto Mancini believes he could have prevented a "big problem" by signing another defender in the last transfer window.
The champions have been without their influential captain Vincent Kompany since he suffered a calf injury in the FA Cup win at Stoke on January 26 and Mancini regrets not bringing in cover.
City did not expect the Belgian to require a lengthy lay-off but his comeback has been put back a number of times and Mancini thinks he should have reacted after a similar experience last year.
The Italian said: "Probably we [made] a mistake because when we knew [of] this problem we were four days to [the] close [of] the market.
"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 but we didn't think that Vinny would stay out for 40-45 days."
Mancini is now hoping Kompany will be fit to return against Newcastle in a fortnight's time.
His prolonged absence has raised fears he could require surgery or miss the rest of the season but Mancini continues to play down the seriousness.
He said: "He has started to run and we hope that he will be ready for Newcastle.
"His calf was tired but he didn't have any problems.
"But we don't want to take a risk at this moment because we have one game and after it is the international break. It is better we wait."
Kompany's absence has seen Kolo Toure, fourth-choice centre-back earlier in the season, return to form and prominence with four successive starts.
The player who seems to have missed out is Joleon Lescott, whose lack of game time cost him his place in the England squad this week.
But Mancini insists the 30-year-old remains in his plans and is continuing to use him, if only off the bench.
He said: "I love Joleon Lescott. Seriously, because Joleon is a top-quality man and a serious, serious professional player.
"He is perfect as a man and as a player. After I can decide if he stays on the bench but this is another story."
When asked if he could understand why Lescott had been left out by England, Mancini said at a press conference: "I don't know.
"But I read all the newspapers pushed for Rio (Ferdinand).
"One manager should take a decision, he has a lot of defenders. I don't know but Joleon is a good player."