NBA to experiment with challenge flag, report says Unknown 00:05 The NBA will experiment with the use of a challenge flag during Summer League games this year. Share this Share on FacebookTweet on TwitterPlus on Google+ Related Posts'Total joke': USADA chief urges WADA to reinstate Russia banFederer, Serena click 'greatest selfie of all time' after dream clashSpurs and Arsenal bounce back with New Year winsSerena Williams posts inspirational message for working mumsManchester City's title hopes bank on beating Liverpool - Bernardo Silva'Fantastic' Djokovic eases to opening Qatar win, Thiem crashes out
