The Hammers, along with Chelsea and Manchester pair United and City, were present during the 21-year-old’s most recent outing.
Manchester United, Manchester City, Chelsea and West Ham United are all said to have scouted Sporting sensation Gelson Martins on Sunday.
According to Portuguese outlet A Bola, the winger’s recent Champions League display against Real Madrid alerted the quartet, who observed his most recent outing against Rio Ave.
And Martins, 21, will likely have impressed, assisting Bas Dost’s consolation in a shock 3-1 defeat for Leões.
The Sporting academy product broke into the first team last season, starting 13 times in all competitions.
However, he has been included in all six of Jorge Jesus’ starting line-ups so far, scoring two goals and making another four overall.
Born in Cape Verde, Martins, who has been capped five times by Portugal’s Under-21s, operates primarily as a right winger, but can also play on the left or through the middle.
West Ham are particularly strong in this area, having added Sofiane Feghouli and Gokhan Tore to a squad which already contained star wide men Michail Antonio and Dimitri Payet.
However, with Tore only on loan, the Hammers may be looking to the future, especially if Payet is prized away from the London Stadium meanwhile.
A Bola reports that Martins’ contract, which Sporting intend to review, contains a €60 million buyout clause.
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