Meaning of “SutaMen(スタメン)”
“SutaMen(スタメン)” means “starting line-up”.
We call “starting line-up” “Start member” as Japanese English.
“Suta(スタ)” is an abbreviation for “Start(スタート)”,
“Men(メン)” is an abbreviation for “Member(メンバー)”.
Example Conversation
A: You belonged to the baseball club in high school?
B: Yeah, but I was a substitute player. How about you?
A: Baseball club too! Basically I was “sutamen(スタメン)”, but our team was really weak and had no chance to win in the official matches.
A: お前、野球部だったの?
B: うん、補欠だったけどね。お前は?
A: 俺も野球部!基本はスタメンだったけど、試合で勝てない弱小野球部だったよ。
Sorry, it’s not really related to スタメン but does being 野球部ベンチ is equivalent to being 補欠 in the club? Or does it refers to something else?
I think your understanding is correct.