Dominic Calvert-Lewin may have picked up another injury after limping off against Leicester City at Goodison Park.
The forward has been hampered by several issues over the past 15 months. He was forced to miss the opening months of the season after picking up a knock on the eve of the Blues' opener against Chelsea.
However, he returned off the bench against Manchester United at the start of last month and scored his first goal of the season during the 3-0 win against Crystal Palace.
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But, and much to the frustration of those in attendance at Goodison, Calvert-Lewin was forced off just after the hour mark after seemingly picking up another knock. He headed straight down the tunnel after leaving the pitch.
It is not yet known what the problem was, but speaking about the possible injury, former Everton winger Pat Nevin told BBC Radio Five Live: "Calvert-Lewin has gone down, he will be replaced. There is no way he will carry on.
"He does get injuries quite regularly and he comes back and maybe wants to push it as quick as he can. No surprise that Maupay is coming on."
Everton trailed 1-0 at the time the forward was replaced, Youri Tielemans' strike the difference between the two sides.
Idrissa Gueye was also taken off at the break, having received treatment during the first half. He was replaced in midfield by James Garner.
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