QUEENS, NY — As tennis champion Coco Gauff knelt on the court with her eyes closed and hands folded, puzzled ESPN commentators were left to wildly speculate as to what Ms. Gauff could possibly be doing. "What do you make of it, Jean?" asked commentator Pam Shriver. "Perhaps it's a new yoga pose? Never seen anything like it!" As Ms. Gauff completed the mysterious ritual and rose to her feet, ESPN producers pored over prior videos. "It appears Ms. Gauff has performed this bizarre practice several times in the past," said ESPN's Bill Bonnell. "We're still at a loss. The...