Bob Bryan Pictures
MADRID, SPAIN - MAY 13: Bob Bryan of the United States about to serve, throws the balls to the court and walks to the net with brother Mike Bryan of the United States to retire in the first set after receiving an injury playing against Nikola Mektic of Croatia and Alexander Peya of Austria in the mens doubles final during day nine of the Mutua Madrid Open tennis tournament at the Caja Magica on May 13, 2018 in Madrid, Spain. (Photo by Clive Brunskill/Getty Images)