"We sometimes put a little bit too much pressure on our backroom staff and ask them to work too many miracles.
"But injuries like this will only improve with time.
"As much as you do treatment-wise, there has to be a certain amount of time - no matter what you do for him to recover.
"We might have been a little bit too hasty in putting a time span on it. It may have been a bit too short, and he might need a bit longer."
Allardyce confirmed striker Matt Jansen, who had his first outing last week in the 0-0 draw against his former club Blackburn, will again be on the bench.
Allardyce said: "The first XI are the most important people to see the game all the way through.
"If we picked up an injury then Matt can go on.
"He's picked up a full week's training and got to know the lads a bit better. We will introduce him if we feel it is necessary."