The 24-year old striker has not yet featured for the Iron this season as he continues to deal with the heel problems that plagued him last campaign when on loan from Liverpool.
Allardyce is keen to get Carroll into his line-up as soon as possible but admits there is no return date from the specialists in Holland who are treating the former Newcastle United star.
"We've been trying to get a date out of the guys over in Amsterdam," he told Sky Sports News.
"But they're reluctant to give us any clear indication of just how long it's going to be before he can join us back here and start training with the players, with the squad and then obviously getting into the team to play some games.
"It's obviously a great worry and concern for us all and one we haven't expected, but one we have to make sure we deal with."
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