The Manchester City midfielder suffered serious ankle-ligament damage during last week's encounter with Tottenham and Capello conceded he was not going to recover in time.
Door is open: After returning for Manchester United, Hargreaves could be in line for a shock England recall
'Too long,' said Capello with a shake of the head. Barry has been an integral part of Capello's plans since the Italian took charge of the national team, not least in the absence of the injured Hargreaves.
But Capello is now expected to turn to Hargreaves as a specialist holding midfielder, even though he has only recently returned from a 19-month spell on the sidelines with a chronic knee condition and has played just one minute of football this season.
Nightmare: Injured Gareth Barry's 2010 World Cup dream is in tatters
Capello was still finalising the 30 names he will announce as his provisional World Cup squad at Wembley later on Monday.
He was awaiting a medical report on Hargreaves, who missed the final game of Manchester United's season on Sunday because of illness, and Bobby Zamora, the Fulham striker who still hopes to play in Wednesday's Europa League final but is struggling to shrug off an achilles injury.
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