Dani Ceballos was allegedly left with a bloodied nose after a training ground incident with Arsenal teammate David Luiz.
While many of their teammates were away on international duty, the pair continued to attend the club's facilities after not being selected by their countries.
According to The Athletic, Luiz took exception to a challenge made by Ceballos on Friday, resulting in a physical exchange.
Midfielder Ceballos is said to have been left with a bloodied nose and a scratch to his face before the confrontation was brought to an abrupt halt.
Although any differences have now been resolved, the report suggests that Mikel Arteta wasted little time in sending the pair home.
Ceballos has taken to social media to describe the report as "fake".