Nottingham Forest striker Taiwo Awoniyi underwent surgery for an abdominal injury on Monday after he clattered into a post during their 2-2 Premier League draw with Leicester City a day earlier, British media reports said.
Substitute Awoniyi rejoined the game after receiving treatment but was limping around for the last 10 minutes.
The club have yet to respond to a request for comment outside regular business hours in Britain.
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Forest owner Evangelos Marinakis expressed frustration over Awoniyi not being substituted, with manager Nuno Espirito Santo saying the Nigeria international was left on due to a misunderstanding between the coaching and medical departments.
Forest, a point behind fifth-placed Chelsea, visit West Ham United on Sunday.