The rift between Manchester City manager Roberto Mancini and his players is widening, with the Italian's absence in the dressing room after Saturday's dismal defeat at Southampton adding to the squad's feeling that they lack leadership.

Mancini sent one of his staff in to collect his bag after a performance which was possibly the worst in his City tenure and then flew home to Italy, with no training planned until today. City's players patently lack a leader in the ranks and some are deeply regretting the loss of Nigel de Jong – one of those players able to rouse and motivate the side – to Milan, when a new contract could not be agreed on last summer.

Mancini will not leave before the end of the season, with chief executive Ferran Soriano and sporting director Txiki Begiristain deciding then whether the club have developed under him this season. But when the pair removed Frank Rijkaard from Barcelona's helm, replacing him with Pep Guardiola, it was because they felt the Dutchman lacked the ability to motivate the squad out of a malaise. Though City's Abu Dhabi owners are averse to being characterised as quick to fire their managers, the chances of Mancini taking the club to a second-place finish and winning a trophy, yet still being dismissed, are substantial.

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A trophy will help his case, even though that is no guarantee of him starting a fifth season, and he seems likely to punish those whose errors cost City at St Mary's, by wielding the axe for Saturday's FA Cup fifth-round tie at home to Leeds United. Reflecting on the lack of heart at Southampton, Mancini said: "I am sure we will change that [against Leeds] because I will change players. I only want players who are ready for the fight in the last 12 games. I am very angry with a lot of my players, and very disappointed at the performance, because it is impossible to play the way we did."

The starting places of Gareth Barry – who has generally been excellent this season – as well as Samir Nasri, who has not, and Edin Dzeko all look vulnerable. Vincent Kompany will return against Neil Warnock's side. Mancini deemed the centre-half's recurring calf injury to represent too much of a risk for Southampton. Matija Nastasic will also return at the back, though it is the midfield, which left the defenders exposed, that Mancini blames for Saturday's 3-1 defeat.

"The gap [at the top] is too much, especially as we are not playing well, have conceded five goals in two games, and can't score," Mancini added. "We need to change more, and have 11 players working on the pitch, not like Saturday, and not like Liverpool [two weeks ago]. Now it is really, really difficult. The gap is too much [and] I am really disappointed. For me, it is not like being an Englishman, who stays calm – I am really angry about this and over the next few days I need to think about what I did, what mistakes I made in the game. After that I will take decisions."

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