The word rival most commonly refers to a person or group that tries to defeat or be more successful than another person or group, which means that rivals tend to come in pairs.
"Right now, I think I have it and I'm not afraid to say it: for me it's Sinner at the moment. That beautiful rivalry that we have, those big games that we have played, on big stages. As the years go by there will be better ones and we will fight for the big titles."
Paris 2021 / Wimbledon 2022 / Umag 2022 / US Open 2022 / Indian Wells 2023 / Miami 2023 / Beijing 2023