The England international was downbeat after Sunday's 1-1 draw at Swansea City which all but confirmed his side's qualification for next season's Champions League.
Manchester City goalkeeper Joe Hart say his team has let itself down in the Premier League this season.
City said farewell to manager Manuel Pellegrini with Sunday's 1-1 draw at Swansea City to gain the point the club required to secure a Champions League place for next season, when it will be led by Pep Guardiola.
Kelechi Iheanacho gave the visiting side an early lead at the Liberty Stadium, but Andre Ayew's deflected free kick beat Hart on the stroke of halftime and the match proved to be the type of frustrating experience that has become all too familiar for England's number one this term.