Feyenoord teammates Miquel Nelom and Tonny Vilhena had to be separated during a training session in Portugal on Thursday after the pair came to blows.
In pictures published by the Daily Mail, 21-year-old Vilhena is seen kicking Nelom, 25, in the penis as teammates rush over to diffuse the row.
Right-back Rick Karsdorp is pictured getting in between the pair as they grab at each other's training bibs before manager Giovanni van Bronckhorst attends to the situation by pulling back Vilhena.
In a post on its Twitter account, Feyenoord said of the training session: "Sparks flew from there in the Algarve and the spicy duels followed each other in rapid succession."
Dutch media reports have suggested that the row began after Nelom made "a strong challenge" on Vilhena.
