Question: Which olympic tennis player, Rennae Stubbs or Juan Martín del Potro, competed in the most Olympic games? 
Sentence (from "Denis Shapovalov"): Denis Shapovalov (Hebrew: דניס שפובלוב‎ ‎ ; Russian: Денис Викторович Шаповалов ; born April 15, 1999) is a Canadian professional tennis player.
Relevant evidence: No