Manchester City's faltering season has been hit by another blow after it emerged Vincent Kompany may miss the remainder of the campaign. The influential captain was substituted during Sunday's 4-2 derby defeat at Manchester United - a result that effectively ended their hopes of retaining their title and left them looking over their shoulders as they attempt to secure Champions League football. And the under-fire Chilean boss, speaking ahead of Sunday's visit of West Ham United, revealed Kompany may not be seen again this term. Vincent Kompany is not guaranteed to return this season after injuring himself in the Manchester derby . Kompany  could have been sent off for a challenge on Daley Blind before being substituted last weekend . 'He is injured,' said Pellegrini. 'It's very difficult to know. He has a muscle injury. We don't know how many weeks. We don't know if he will be fit from now until the end of the season.' Pellegrini claimed he did not feel under pressure despite speculation mounting that he may be sacked at the end of a disappointing year. Manuel Pellergini claims he is not concerned by the mounting pressure over his position at the Etihad . Bundesliga managers Jurgen Klopp (left) and Pep Guardiola have been linked with a move to City . 'My pressure is always the same,' he said. 'To try and win every game. Last year (there) was more pressure when we were fighting for the title. It's the worst moment but the pressure to recover is not same.' He added that he was not hurt when he heard other managers such as Bayern Munich boss Pep Guardiola and departing Borussia Dortmund manager Jurgen Klopp linked with his own job. 'Every time you manage an important club, every big club, if you don't have results the club deserves everyone talks about changing manager. I trust a lot in the work I do. Nobody is happy with results. It's not logical to sack the manager. I don't think that's the right diagnosis.' The reigning champions have slipped from serious title challengers to fears over not finishing in the top four . Pellegrini added that he took the blame for a record that his seen City win just four of their last 15 matches. 'It's always my responsibility for the squad. I choose the players. I always trust my players and its always my responsibility.' Pellegrini is also expected to be without long-term injury victims Stevan Jovetic and Wilfried Bony for the visit of Sam Allardyce's Hammers. He added that James Milner (knee) and Gael Clichy (groin) would also miss out.
Vincent Kompany was injured in the Manchester derby defeat by United .
Manuel Pellegrini is not sure if the Belgium star will return this season .
The Premier League champions face West Ham at the Etihad on Sunday .