He is still gaining experience on the farm team.
The second-team games have fewer spectators than the first team.
His strong play was recognized, and he was promoted from the second team to the first team.
一軍 is the top-level first team, while 二軍 is the reserve or developmental squad below it.
Compound of 二 (second) and 軍 (army, team), originally from military terminology, now common in sports.