Sunday's 1-0 defeat by Tottenham Hotspur sent Everton F.C. down to sixth in the Premier League, five points behind Liverpool F.C. in fourth spot with 13 matches remaining.
Everton F.C. dominated the match at White Hart Lane, but were undone by a clinical finish by Spurs forward Emmanuel Adebayor in the 65th minute.
With on loan striker Romelu Lukaku sidelined by an ankle injury, Lacina Traore still coming up to speed since his arrival in January and Nikica Jelavic now at Hull, manager Roberto Martinez was forced to play Kevin Mirallas up front.
While full of skill and guile, the Belgian is better suited to playing out wide, and the lack of a target man was a factor in the defeat, according to England's Jagielka.
"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."
Everton play Crystal Palace on Wednesday and Martinez said they would seek to take their frustration out on opponents who have won six out of 13 league matches since Tony Pulis replaced Ian Holloway to rise to 14th.
"It is important we focus now on Crystal Palace and we will try to get rid of the frustration in that performance," the Spaniard said.
"There are many games left and there will be many twists and turns. What we can't do is get too disappointed by the scoreline.
"Obviously we want to win games but our performance merited a good scoreline. When you do that it is a matter of keeping playing good football and the points will come."