The Hammers were well positioned to challenge for a European place at the end of 2014, but they have seen their form slump since the turn of the year as they have won just once in their last 11 top-flight matches.
As a result the club have dropped into 10th place in the Premier League much to the frustration of Allardyce, who feels that his squad have lacked enough depth to sustain their strong start to the campaign.
"The sad thing is we've forgotten how to win," he told the club's official website. "To not have got over the line in recent games is massively disappointing for everybody concerned.
"The entertainment value is there, the attacking play is exceptionally good and the opportunity to win games has been there on at least five occasions in the last 11 games. So, instead of competing for a European place as we should be doing, we're now sat in 10th hoping to stay in the top half with 10 games to go.
"Our need to try and win games from winning positions has just failed us recently. Factors in terms of disruption through suspensions and injuries and loss of form mean that, squad-wise, perhaps a finish in the top eight needs a bit better quality of player or more strength in depth."
West Ham face Arsenal in the Premier League later today at the Emirates Stadium.