Everton have suffered a major injury setback as £25m summer signing Jean-Philippe Gbamin will face at least eight weeks out with a thigh injury.
The 23-year-old Ivory Coast midfielder, who signed from Mainz, featured in Everton's opening two league games.
But he missed Friday's 2-0 loss to Aston Villa after sustaining what the club described as a "significant" injury in training.
Toffees manager Marco Silva said it was "more significant than expected".
Gbamin will have further tests this week with a worst-case scenario of 12 weeks out, although it is hoped there will be no need for surgery.
Everton signed Gbamin and Fabian Delph to fill the gap left by Idrissa Gueye's departure to Paris St-Germain. It is hoped England midfielder Delph, signed from Manchester City for £8m, will return imminently after a groin problem picked up in pre-season.