I was what we used to call, and probably still do call in schools, a " bench warmer." The " bench" is the place where the team's players who are not playing sits.

我是我们过去常说的， 在学校里可能仍然这样称呼我，“板凳暖手” 。 “板凳” 是球队不上场的球员坐的地方。