on the sidelines 場外、外野

on the sidelines はコートの外のサイドライン、つまりゲームに参加していない状態やメインイベント以外のサブイベントを指したりする。stay on the sidelines, sit on the sidelines, stand on the sidelines,,,色々な組み合わせが可能だ。 1:46 I want to thank the women of Japan for inspiring me to believe even more strongly that "when women succeed nation succeed(s)." a great change is taking place. and I have total confidence in the ability of Japanese women to lead this country. I want to thank the teachers, business leaders and family members who are supporting and mentoring them and who realize that they are too talented to sit on the sidelines.

Ambassador Kennedy Farewell Message / ケネディ大使から日本の皆さんへ御礼のメッセージ

https://www.youtube.com/watch?v=X6W7xi4QokE  1:22 he's not commenting. he's sitting on the sidelines. パパ・ブッシュはヒラリーに投票、甥っ子ブッシュはトランプ派だが、肝心のジョージ・ブッシュといえば、ノーコメントでだんまりを決め込んでいる。
Will Bush family vote for Trump?

https://www.youtube.com/watch?v=L3cBY1CyUR0  0:30 I'm standing on the sidelines of a CrossFit class in Boulder, CO. totally intimidated. コロラド州のジムにきてみんなの運動する姿を眺めていますが、迫力がありますよ。
The death of the peanut

https://www.youtube.com/watch?v=8A6zqNqmXW0  1:27 on the one hand, China is showing patient, sitting on the sidelines while the disruptive Occupy movements spread.
Hong Kong rejects democratic reforms | FT World

https://www.youtube.com/watch?v=m_iS_4elIjg  3:30 the soldiers watch nervously from the sidelines.
Chavez inauguration postponed

https://www.youtube.com/watch?v=dQAPX5N5-P0  0:12 shy little Paris is still on the sidelines while Phoenix is enjoying some rough-and-tumble play with his brother.
Playful Spaniels | Too Cute!

https://www.youtube.com/watch?v=9XkFC55qtaA  0:13 meeting on the sidelines of the Summit in Panama パナマでの米州首脳会議の時間の合間を見てオバマ大統領とカストロ議長が初会談をした。
Obama and Castro make history with US-Cuba talks

参考リンク
http://bridge-english.blogspot.jp/2014/04/blog-post_6722.html  わたしの城下町
http://bridge-english.blogspot.jp/2014/04/blog-post_4057.html  中立を保つを英語でなんと言うか？

練習問題解答
b-3419 on the sidelines
b-4701 sitting on the sidelines