City need Hart to stay fit for the next month as Shay Given's long-term shoulder injury means that they only have unfancied Stuart Taylor as cover.
But the England number one missed the second half of training at Carrington on Wednesday after his back seized up midway through the session.
Fine form: Joe Hart (grounded) impressed against Manchester United on Saturday
Hart has suffered sporadically with back trouble this season and City must hope now that he recovers in time for Monday's Barclays Premier League visit to Blackburn.
City remain hopeful that captain Carlos Tevez will be fit for the FA Cup Final against Stoke City on May 14 and have now pencilled in the league game against Everton a week earlier as his provisional comeback date.
Tevez is still receiving treatment on his torn hamstring in Milan from the Argentina national team doctor. He is expected to return over the weekend.
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?Explore more:People: Carlos Tevez, Stuart Taylor, Shay Given, Joe Hart Places: Milan, Argentina, United Kingdom
Source: Daily Mail
Source: Daily Mail