West Ham, who have 33 points from 29 matches, dropped two places to 14th following the 2-0 defeat at Chelsea and, but for Jaaskelainen, the home side could have won more emphatically.
Jaaskelainen said: "Players like Mata and Hazard are top-class but the way we kept the ball in the first half wasn't good enough. We were a little bit lucky not to concede more.
"We just have to keep going. We have a weekend off now and then we have to go again in a massive game against West Brom in a fortnight."