The 23-year-old Oviedo stepped off the mound, pulled out a laminated card from his back pocket to presumably change up his signals, and then definitely yelled "shut the f—k up!" at Yastrzemski, who pretended to act bewildered.
After the 5-2 Giants victory, Oviedo told reporters he thought Yastrzemski "was giving some signs," but admitted "it was a misunderstanding there." Which is true, though only to an extent. Yastrzemski wasn't just innocently minding his business! He was very much messing with the 23-year-old pitcher.