Marouane Fellaini will miss the next three games after headbutting Ryan Shawcross, while the Toffees are also set to be without Victor Anichebe, Kevin Mirallas, Phil Neville and Tony Hibbert in the upcoming weeks.
Ahead of Everton's trip to face West Ham on Saturday, Jagielka told The Liverpool Echo:"It's not like we have had massive squads in the past, it is par for the course that we have 16-18 senior players,
"It will test our squad because it is always a busy time but the manager knows what he is doing and if someone needs rest then I'm sure they'll get it.
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"We just have to get some much-needed points to keep us at the top of the league."
The Toffees are currently sixth after 17 games, and are only two points off the Champions League places.
The England international remains cautious at this stage, however, and is hoping Everton can show their typical strength in the second half of seasons once again this term.
He continued: "We don't want to be looking too far ahead - we normally have a good second half to the season but that is not a guarantee.
"The manager will be nervous now because this is where our season normally starts.
"It would be nice to put two parts of the season together rather than just one."