The Merseyside outfit fell a 1-0 defeat at fellow top-four hopefuls Tottenham on Sunday, with Emmanuel Adebayor's goal in the second half settling matters.
Defeat was somewhat harsh on an Everton side who enjoyed the better of large spells of the match, but Roberto Martinez's men were unable to break through the Tottenham defence, with winger Steven Naismith starting as an auxiliary forward in the absence of Romelu Lukaku, Lacina Traore and Arouna Kone.
January loan signing Traore was only fit enough for a place among the substitutes at the weekend, while Lukaku remains sidelined with an ankle issue and Kone is a long-term absentee with a knee injury.
Everton are now five points adrift of fourth-placed Liverpool, and Jagielka feels their lack of an out-and-out striker proved the difference at White Hart Lane.
"We're struggling a little bit at the moment," he told the Liverpool Echo. "Lacina is not quite right yet and it's difficult because although we played some good stuff we were perhaps missing that fox in the box or target man to get us the goal.
"It's frustrating and at the least we should probably have kept a clean sheet and come away with 0-0 but we didn't.
"It's going to be a little bit harder for us now, there are other teams in the mix for fourth.
"If we'd beat Spurs we'd have pushed on a little bit, but there's still 13 games left and a lot of points to play for.
"A lot of teams are trying to get as many points as they can for one reason or another and we've got a lot of hard games too."
