Having been involved in a relegation scrap for much of the season, the Hammers now hold a comfortable position in the Premier League table, 10 points clear of the drop zone in 11th.
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"When they all got fit we knew we'd be a better team and a better squad," Allardyce told reporters.
"At the end of the day, a lot of your team depends on how good your centre-forwards are and when they're available. Missing Andy Carroll for so long has always been hard.
"As good as Carlton Cole has done, particularly - he's scored six goals this year - Andy Carroll is one of our main investments, one of our best players who can upset defenders and can score goals.
"When you haven’t got him for so long that can have an effect on the team.
"You can play as well as you like between one end of the pitch and the other but if you haven't got anybody who can create or score goals then that becomes a problem for results."