The 32-year-old full-back has started all three of the Hammers' Barclays Premier League fixtures so far but, even though the defence has leaked just the solitary goal, Sam Allardyce's side have only picked up four points.
An opening day 2-0 win over Cardiff was followed by a goalless draw at Newcastle and a 1-0 home defeat to Stoke.
Demel admits the whole squad were upset with the loss to Mark Hughes' side but knows there is very little that needs to change to alter West Ham's fortunes.
"We lost our last game at home, and we didn't expect that so early in the season after our home form last year," he told the club's official website.
"So of course it is a disappointment, but if you look at the season so far we've only conceded one goal, from a set piece.
"Newcastle had one shot against us away from home, so defensively we're in good shape. Now we have to make sure that when we keep the ball, we capitalise on our chances.
"We'll work on that, the Premier League is the best league in the world, so when you have the chance to punish the opposition you have to take it."