The former Swansea City, though, has praised the 27-year-old striker for his recent performances.
The Senegal international scored for the Toffees in their 3-1 victory over Crystal Palace at Goodison Park in the Premier League at the weekend.
Niasse has scored seven goals and provided two assists in just eight league starts for the Toffees so far this campaign, having initially struggled for playing time under then manager Ronald Koeman.
Sigurdsson told Everton’s official website: “Oumar has been fantastic. It was obviously very tough for him at the start of the season.
“But he has come in, worked really hard and scored some really important goals for us. Hopefully that will continue.”
Everton have been crying out for a proven goalscorer since the start of the season, and although the Toffees signed Cenk Tosun form Besiktas in the January transfer window, it is Niasse who is banging in the goals at the moment.
The 27-year-old is not exactly a ‘great’ footballer, but the way he has established himself as an important player in Sam Allardyce’s team is remarkable, and his determination must be lauded.
Niasse has been on the books of Everton since February 2016 when he joined from Lokomotiv Moscow for a transfer fee reported by BBC Sport to be worth £13.5 million.