Manchester City fear playmaker David Silva will require surgery on a troublesome ankle problem at the end of the season, [football] direct news understands.The Spaniard, who has mustered more assists than anyone in the Premier League over the last two seasons, is unable to train more than twice a week and is playing through the pain barrier.He is due to be a key part of his national side’s World Cup campaign this summer and, while the Blues have no intention of blocking his participation in the tournament, a source close to the Etihad Stadium told FDN there are concerns that he will return from Brazil in need of an operation.Should Spain progress to the final stages of the competition, the 29-year-old could miss the start of next season if it transpires that he does need to go under the knife.It is the second successive campaign that the ex-Valencia schemer has been hampered by ankle trouble, although this term he has returned to his best form after a difficult period during previous boss Roberto Mancini’s final year in charge.Silva is still expected to start in Sunday’s crunch clash with title rivals Liverpool at Anfield.Watch the second leg of UEFA Champions League quarter-final: Borussia Dortmund face Real MadridRead more Manchester City transfer news.