(n.) One who emulates, or strives to equal or surpass.

adversary amateur athlete antagonist archer athlete ballplayer baseballer baseman batter battery battler belligerent belted knight bickerer blade blocking back bowman bravo brawler bully bullyboy catcher center coach combatant competition contender contestant corrival cricketer defensive lineman disputant duelist emulator end enforcer entrant fencer feuder fighter fighting cock foilsman footballer gamecock games-player gamester gladiator goon gorilla guard hatchet man hood hoodlum hooligan infielder jock jouster jumper knight lineman militant offensive lineman opponent opposition outfield outfielder player plug-ugly poloist professional athlete pugilist quarreler quarterback racer rioter rival rough rowdy ruffian sabreur scrapper scuffler skater sport sportsman squabbler strong arm strong-arm man strong-armer struggler swashbuckler sword swordplayer swordsman tackle tailback the field thug tilter tough toxophilite tussler vier wingback wrangler wrestler