Mancini: Missed chances to blame
City reduced United's lead to a still formidable 12 points with a 1-0 success at relegation threatened Aston Villa Monday night courtesy of Carlos Tevez's first half goal in stoppage time.
But City manager Mancini acknowledges a failure to overcome other struggling opponents this season, despite carving out plenty of chances, has been a key factor in their downfall.
He said: "At Southampton, we played very well and we lost (3-1). We had other games like the one at Villa - against QPR and West Ham - where we missed four or five incredible chances.
"Even in the Villa game, we had other chances to close out the match rather than winning 1-0.
"It has been our problem this year and has cost us points.
"We have a lot of chances in every game that we are missing. This is the difference at this moment (from last season)."
Mancini concedes City may need to win their remaining 10 games to have any hope of overhauling United.
But he will be without midfielder Jack Rodwell for the first part of that demanding task after he suffered another setback to his long term hamstring problem at Villa Park.
Mancini confirmed Rodwell will be sidelined for "three to four weeks" after being substituted during the first half.
He said: "Jack was distraught in the changing room. I am very sorry because he is such a promising young player.
"He needs to improve but he had played very well against Chelsea in the previous game and had been playing very well at Villa."
The City chief is hopeful striker Sergio Aguero will be back available for the next league game with Everton but has ruled him out of the weekend FA Cup tie against Barnsley with a knee injury.
Villa remain in the bottom three but Mancini had words of encouragement for his counterpart Paul Lambert and believes his young side are capable of staying up.
He said: "I believe they are a good team. I think they can stop up. The problem they have is they have young players.
"But if they are able to stay in Premier League, next season I think they can enjoy a good season.
"When you are a young team, maybe you can have some problems. But after one year I think they can improve.
"I like Christian Benteke, Charles N'Zogbia, Andreas Weimann - all these players."
Villa's attention will now turn to a crucial double header with a visit to fellow strugglers Reading on Saturday and a home clash with QPR the following weekend.
Lambert is confident Villa can survive if they maintain the level of performance seen when losing by the odd goal to Arsenal and City in their last two games.
He said: "The lads know they are playing well and that's why they are going into games full of confidence.
"It's different if you are coming away from games having been beaten heavily.
"But the last couple of months they have been playing well without getting the rewards. Hopefully the rewards will come."
A mistake by Ciaran Clark seconds before the interval resulted in Tevez sealing City's seventh away win of the campaign.
Lambert said: "I just had chat with him at half-time. It is easy go in and absolutely take the paint off the wall. I knew that wouldn't do him any good.
"I thought he responded brilliantly in the second half. He didn't let it affect him, which was great and he has been excellent for me this season.
"But when you're playing at this level and you make mistakes with the calibre of strikers you're playing against, you know what can happen."