中堅(ちゅうけん)nucleus, backbone, mainstay, key figure, medium-level, mid-level, middle-ranking, midsize, main body (of troops), crack troops, select troops, center field, centre field, center fielder, centre fielder, athlete competing in the middle-number match in a team competition, i.e. second in 3-on-3, third in 5-on-5 (kendo, judo, etc.)