Calvert-Lewin returned to the bench against Chelsea following a quad injury. The striker has endured a difficult season because of various setbacks.
Meanwhie, Yerry Mina was back in the starting line-up after he was rested for the defeat to Liverpool the previous weekend.
The Colombia international only recovered from a long-term quad issue recently and is being carefully managed.
Now with a clear week of training before making the trip to Leicester City on Sunday, Lampard's aiming to improve Calvert-Lewin's conditioning.
What’s been said
The Everton boss told the club's website: “With Yerry, I’m delighted he’s come back into the fray in terms of his fitness.
“You can see that leadership, presence and personality he brings. He is a big leader for us. It was great to see him play like that.
“We have a week now [before the Leicester game] to get Dom more fit, because he can be a big player for us – we know that – and to keep the levels in the squad high and positive.
“We have five big games left and still have a lot of work to do.”