Reilly Opelka faces potential discipline for his post-match comments about a chair umpire he called the “worst ump on tour,” the ATP said in a statement Friday. Opelka was angered that he received a point penalty while serving for the match in the third set against Cameron Norrie at the Dallas Open on Thursday night. Opelka went on to win 4-6, 7-6 (5), 6-4.