According to reports from Portuguese media outlet A Bola, West Ham representatives have watched Portimonense star Shoya Nakajima in action on Friday evening.
The 24-year-old winger joined the Portuguese side in the summer transfer window from FC Tokyo, and has made a strong impression already.
He has scored five goals for his new club, and has been watched by the likes of Manchester United, Napoli and Borussia Dortmund.
The publication claim that West Ham had a representative at Estadio Municipal on Friday where the winger played his part in helping his side win 3-1 against Vitoria Setubal.