Sean Dyche says Dominic Calvert-Lewin faces a dual challenge of getting over his hamstring issue and becoming "genuinely fit so his body doesn't break down".
The Blues striker was absent from the matchday squad for the Merseyside derby after playing an hour in Dyche's first game against Arsenal. He had been described as "touch and go" in the build-up to the fixture but missed out with academy graduate Ellis Simms starting in his place.
What happens next for Calvert-Lewin is likely to be crucial to Everton's season and the club's Premier League survival hopes but Dyche stressed he will not risk the 25-year-old's long term health by rushing him back.