The WhatsApp message arrived mid-match. Anthony Amalraj was sitting courtside at the 2018 Commonwealth Games in Gold Coast, Australia. On the other side of the world, in a room in Delhi, coach Sandeep Gupta was watching the semi-final on television. Manika Batra was trailing against Feng Tianwei, the World No. 4 from Singapore. Gupta spotted something. A flaw in how Feng was returning serve. He typed a note on his phone and hit send.