Although Sir Alex Ferguson's team have seamlessly climbed above Manchester City and Chelsea to reach the summit in recent weeks, the Scot has regularly bemoaned the standard of his team's defending this season. The Red Devils have conceded just short of 29 goals per season over the last five years, but they have already conceded 19 this term after just 13 matches thanks to a mixture of injuries to key players and sloppy errors by those who have featured. Allardyce, whose side lost 3-1 at Spurs on Sunday, admits West Ham will face a big task if they are to win, but he takes comfort from the fact that the days of regular shut-outs at Old Trafford are now rare.
"Manchester United have leaked a few more goals than normal," Allardyce said.
"Their defensive qualities haven't been as good as they have been over the past few years.
"The problem is at the other end they never stop scoring goals, but if we can get our defensive unit on song and if we play as a team in and out of possession then you never know what will happen."
The controversial chanting that came from West Ham supporters during the game at White Hart Lane drew attention away from what was arguably the worst league performance of the Hammers' season. Allardyce's men had climbed to joint sixth in the table after making a surprisingly good start to the season, but they lacked pace, ideas and concentration against Spurs, who ripped them apart with ease. With games against Chelsea, Liverpool and high-flying West Brom coming up, Allardyce knows his team are in danger of slipping into the bottom half of the table, but he thinks his players will bounce back with a better performance at United.
"The team did brilliantly when we drew against Manchester City and beat Newcastle so let's see if they can do it against Manchester United, Chelsea, West Brom or Liverpool," the 58-year-old said.
"There is no real pressure on the lads. It's a match they will enjoy. It's a game they will have dreamed about since they were kids.
"If we give a good account of ourselves then hopefully it will be good enough to get us something from the game."
Another disappointing factor of Sunday's defeat was that Mark Noble picked up his fifth booking of the season and is therefore suspended tomorrow. In truth the only plus point from last weekend for Allardyce was that Andy Carroll ended his 1,062-minute Premier League goal-drought. Allardyce hopes the £35million striker, on loan from Liverpool until the end of the season, now starts scoring on a more regular basis.
"One of the things we have been really good at has been providing service and opportunities to lots of players to score," Allardyce added.
"Our problem has been everyone, not just Andy, converting those chances. I hope he kicks on now."
Allardyce also has doubts over left-back George McCartney, who suffered an ankle injury against Tottenham, while Yossi Benayoun's persistent thigh problem means he will once again be missing tomorrow. West Ham's injuries mean Allardyce may be forced to enter the transfer market in January. He has already expressed an interest in signing Nicolas Anelka from Shanghai Shenhua while another big-name star - David Beckham - has also been linked with a possible return to east London, where he was born. Allardyce was coy on whether a move for Beckham would be possible today.
"I haven't heard from him. I don't know what David is thinking or doing at the moment," the former Bolton boss said.
"We will wait to see what he's doing and then we will see what happens."