Sam Allardyce has braced West Ham for the biggest test of their Premier League season when Arsenal arrive at Upton Park.
The Hammers have made a strong start on their return to the top flight and sit seventh in the league, with three wins and two draws from their first six matches.
Allardyce's men are one place above north London rivals Arsenal - but he knows their honeymoon period is over.
West Ham face all of last season's top six clubs within the next two months, starting with the Gunners, in a period that could define their campaign.
"We have 11 points from six games so we are delighted that our start has been as fruitful as it has been," Allardyce said.
"They (Arsenal) are a top four side. This is a big test for the players and whether they can master the quality of opposition.
"Can they understand what they need to do or change their game slightly to get best chance of a result?
"Arsenal are so good at keeping the ball. We will need to concentrate that they don't get behind us. That is a key area.
"We need to accept that we won't see the ball as much as other home games, Villa, Fulham and particularly Sunderland."
Allardyce will decide today whether or not to start with England striker Andy Carroll, who has returned from a hamstring injury but remains short of match fitness.