One need not be particularly interested in sports to find Luca Guadagnino's new tennis drama, Challengers, compelling. Guadagnino frames his tennis matches as either gladiatorial blood sports or sex, and sometimes both at the same time. Tennis is a relationship, Zendaya's Tashi Donaldson explains; and indeed, the tennis matches here are often thinly veiled stand-ins for dialogue the characters are either unwilling or unable to have.