Everton have been boosted by the news that Dominc Calvert-Lewin's hamstring injury is not as serious as first feared.
The England striker will miss Sunday's match against Fulham after being taken off with the problem in the midweek 5-4 FA Cup victory over Spurs, but will be back for the visit of Manchester City next Wednesday.
Ancelotti had initially thought "something wasn't good," but he is relieved that his top-scorer will miss only one match due to the strain.
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He said: "Dominic only had a sensation in his hamstring, a feeling that something wasn't good. However, it is only a little problem and he will be able to play on Wednesday (against Man City)."
Goalkeeper Jordan Pickford will also return for that match and sits out Sunday's match with Fulham alongside his England team-mate Calvert-Lewin.
Josh King will replace Calvert-Lewin in the line-up this weekend, and make his first start for the club after signing from Bournemouth on Deadline Day.
Meanwhile, Ancelotti says Lucas Digne has agreed a new contract at Everton and is set to officially sign the extension next week.
The France international, who signed from Barcelona in 2018, sees his current deal expire in 2023 and he has been tracked by bigger clubs across Europe.
Ancelotti says terms have been agreed with 27-year-old Digne, who captained the club for their 3-3 draw at Manchester United last weekend.
"I'm not in there but I know that they agreed, then next week I think they are going to sign officially the new contract," Ancelotti said.