Sam Allardyce believes Arsenal have struggled this season because they have failed to replace Robin van Persie adequately.
Successive defeats against Manchester City and Chelsea have dented Arsenal's confidence. Now Allardyce, who has yet to register a single away league win against Arsenal as a manager, hopes his West Ham side can take advantage of their London rivals' poor run in tomorrow night's match at the Emirates, rescheduled from Boxing Day owing to a Tube strike.
"When you sell your best players, which is not normally expected of Arsenal, then it's always difficult to replace them," he said.
"The players who have come in are very good players but are they better than the ones they have sold? Selling players for £24m means it's a big ask, even for Arsène Wenger with his huge recruitment policy, to replace those players immediately. That's why they've suffered in terms of the results they've been getting. The football is still very good but when you lose that amount of goals as they did with the loss of Van Persie, that will happen."
"I'm sure he is frustrated because he has been the best manager that Arsenal have ever had," Allardyce added. "From our point of view, we hope with the disappointment of that result against Chelsea that there might be a little lack of confidence in the players that play. If that's the case then we might have a chance of getting a result."
West Ham, who have also struggled to repeat their early-season form and have scored only five goals away from home in 10 league matches, will be without Marouane Chamakh owing to the terms of his loan from Arsenal, meaning Carlton Cole should start up front. Andy Carroll is close to making his return after six weeks out with a knee injury but Allardyce has no plans to rush him back.
"He's training on a daily basis now and he will have joined in, hopefully, by the end of the week, or certainly the beginning of next," Allardyce said.
"If needed against Fulham next week he might be considered but, obviously, he won't have played a game for a long time. In the end it's better that we get him fully fit this time and make sure he stays fully fit now until the end of the season."