Both:
https://www.mangago.zone/read-manga/salad_days_tang_liuzang/ (boxer & ballet dancer)
https://www.mangago.zone/read-manga/surge_looking_for_you/ (swimmer & ice skater)
https://www.mangago.zone/read-manga/the_keystone_romantic_combination/(baseball players)
https://www.mangago.zone/read-manga/contradict/ (not athletes in the traditional sense, but I’d consider a firefighter to be similar enough)
https://www.mangago.zone/read-manga/ballboy_tactics/ (retired gymnast & basketball player)
One of them:
https://www.mangago.zone/read-manga/sweet_spot_se_yang/ (baseball player)
https://www.mangago.zone/read-manga/dash_team_hazama/ (retired swimmer, but very sports related still)
https://www.mangago.zone/read-manga/off_track/ (racer)
https://www.mangago.zone/read-manga/onward_1/ (swimmer)
https://www.mangago.zone/read-manga/the_tiger_who_swallowed_the_moon/ (Olympic shooting)

any BL recommendations where both (or one) are athletes?