Carroll has been plagued by fitness setbacks since arriving at West Ham permanently from Liverpool in June last year and underwent ankle surgery this July.
The forward came through 90 minutes in Saturday's 2-1 defeat at Goodison Park for the first time since a 1-0 loss at West Brom back in April.
West Ham manager Allardyce turned to Carroll in the absence of Enner Valencia (knee) and Diafra Sakho (back), who have made an impressive start to life at the London club.
Allardyce had not planned to keep Carroll on for the duration on Merseyside, but was left with little option and hopes the 25-year-old will soon be firing on all cylinders as he builds up his match fitness.
"Andy's fiancee is the owner of a gym and a yoga centre and many times in his striving for fitness he's spent some time with her," he told the club's official website. "She's helped him not so much get fit, but stay in good condition.
"We didn't want to play him for 90 minutes as he's not quite ready for 90 minutes, but because of circumstances it had to be that. He coped with it well and we know he's going to get better the more match fit he gets.
"With the opportunities of other strikers putting pressures on Andy he's got to get on top of his game. The way Enner Valencia and Diafra Sakho have played this year, they've put big pressure on Andy and even Mauro Zarate's performance as sub was really good.
"Andy doesn't feel any pressure - he looks after himself and thinks he should play every week and rightly so. At this moment in time he has a little way to go to find his full match fitness. He did very well for us to complete the 90 minutes.
"We hope this final operation will be one of the major reasons for him not having the same injury problems as he's had over the last couple of years."
