Roland Garros, Berrettini perplexed in the match against Arnaldi: what happened with the umpire?

A curious incident occurred during the Roland Garros quarterfinal match between Matteo Berrettini and Matteo Arnaldi today, Wednesday, June 3. During the eighth game of the first set, Berrettini was stopped twice in a row by the chair umpire for a foot fault during his service game.  

Berrettini, visibly perplexed, first turned to his corner and then, after the umpire's explanation, saved five break points during the game, managing to hold serve at the end of a 16-minute marathon game.  

(Adnkronos)