The diminutive (by tennis standards) Belgian David Goffin secured the biggest win of his career beating the current world No.1 Rafael Nadal in his opening match at this year’s ATP Tour Finals at London’s O2 on Monday. Rafa was hampered by a reoccurring knee injury which forced him to withdraw from the year-ending tournament after the three-set loss. David, who is currently ranked No. 8 in the world has won four titles and his win over Rafa continues a string of victories over higher-ranked players, including Novak Djokovic and Stan Wawrinka. He signed my sketch at the O2 on Sunday before his practice session.