Question: Which olympic tennis player, Rennae Stubbs or Juan Martín del Potro, competed in the most Olympic games? 
Sentence (from "Juan Martín del Potro"): He was the first to defeat both Federer and Nadal during the same major and was the only man outside the Big Four to win a major between the 2005 French Open and the 2013 US Open, a span of 35 tournaments.
Relevant evidence: No