fielder
Baseball term for any defensive player, including infielders and outfielders. Contrasts with 投手 (pitcher).
彼は高校時代、野手として活躍した。
He played an active role as a fielder in high school.
He played actively as a fielder and contributed to the team's victory.
Check the fielders' defensive positions.
The manager put the rookie in as a fielder.
投手 is the pitcher, while 野手 refers to any defensive player other than the pitcher (and catcher, depending on context).
内野手 specifically means an infielder, while 野手 is the broader term covering both infielders and outfielders.
外野手 specifically means an outfielder, while 野手 is the broader term covering both infielders and outfielders.
counter for people
Compound of 野 (field) and 手 (player), literally 'field player'. A straightforward baseball term.