Question: Who is a considered a better tennis player, Martina Navratilova or Jack Sock?
Sentence (from "Martina Navratilova"): Martina Navratilova (Czech: "Martina Navrátilová" ] ; born Martina Šubertová ] ; October 18, 1956) is a former Czechoslovak and later American tennis player and coach.
Relevant evidence: Yes