Banayoun, a £5m summer signing from Liverpool, has been booked in for surgery on Monday and may not return to action until mid-April.
The Israeli ruptured his Achilles during training while on international duty last week and was sent back to west London for further tests. Former West Ham star Benayoun, 30, is now tipped to be treated by the same Icelandic surgeon who repaired David Beckham’s tendon earlier this year.
Benayoun has only made six appearances and is yet to start in the Premier League since swapping Anfield for Stamford Bridge in July.
His chances of establishing himself this season look to be all but over, however, as Chelsea could have only half a dozen games left by the time he is well enough for first-team football again. It is also a blow to the double winners, who are still without England midfielder Frank Lampard.